Well, I think you've actually touched on where the disconnect lies between what we're saying and what he's saying.
He seems to be saying that there is exactly one sense or one set of circumstances in which you can claim someone made an explicit statement.
You disagree with that and so do I.
So, for example, say you were speaking to someone and trying to hold them to some comment or agreement they made and you said to them, "You explicitly told me ... x."
It seems Sulla's position is that, in saying the person explicitly told you x, you must mean the person made a statement containing a series of words that each have only one possible meaning, and their organization in the actual statement can, in an absolute sense, literally have only one meaning.
While this would certainly be an unassailable example of an explicit statement, I think it takes a hyper-literal approach that is problematic in the same way it was problematic to argue that you cannot use something abstract as the genitive substantive in a partitive genitive because abstract things don't literally have parts into which they can be separated. In other words, it ignores the way in which people use, absorb, interpret, and understand language.
So, I think the position that you and I share, Rotherham, is that you could say to a person "You explicitly told me ... x," and what you mean is that in the context of your discussion with that person, and based on the language that person was using throughout that discussion, there was simply no other reasonable way to interpret their statement. If you went through that discussion 10 times, you would interpret the statement exactly that way every time, even if technically the words could mean something else when transposed into a different context or setting. This is so because all those things upon which sensible, intentional communication from one person to another is built would, in that context, be pointing towards one particular meaning.
These are the types of statements that if you were to call someone on them and they would try to say that they meant something else you would insist that they were being disingenuous and equivocating, either when they said it initially or when trying to apply a different meaning to it now. You would insist this, because there was no reason for you to understand it in any other way than you did, and there could be no reasonable expectation on their part for you to understand it any differently.
Our position is that Rev 3:14 explicitly identifies Christ as the first creation in this second sense. We do not mean that if you were to take the group of words forming the sentence, put them on a piece of paper and hand them to some random translator, that there would be literally and absolutely only one possible way to translate or interpret them (though I'd wager that if "by God" was changed to something like, "by Paul," at least 99% would translate and interpret it just as we say it should be).
What we mean is that when those words appear in the context of John's writings and the NT as a whole, there is only one reasonable way to translate and interpret them. To assign a different translation or meaning is to argue that John (and/or God) intended to convey his message in a way that was communicatively nonsensical, in that it has John utterly ignoring the way in which people naturally understand the language being directed at them from some particular source. It amounts to verbal or literary trickery. If you say a word over and over and over again with a particular meaning, then you train people to understand you a certain way. Every time you use that word, they are going to default to understanding you that way, unless it is used in a context where you obviously CAN'T mean it that way.
In Sulla's challenge, as I recall, he tried to argue that he could write a book and use the word "bank" a thousand times to refer to his local banking establishment, but that wouldn't prevent him from one time saying that he was going to go fish in the shade on the bank. But this is clearly an example of what I said right above would be required to have the audience understand he intended to use the word in a different way. In fact, I think he even said it was obvious that he was using the word with a different definition in mind. And that's precisely the point. The statement itself makes it obvious that he intends to use the word with a different meaning. The semantic change is clearly and unmistakably signaled in the statement itself. This is precisely what good authors do so that their audience can understand them. It's a matter of simple communicative logic.
But consider the mistake that an extremely poor author might make in failing to apply this simple communicative logic. Let's say the author wrote a book in which he used the word "bank" a thousand times. 999 of those times, he used it to mean his local banking establishment, but in its 987th occurrence in the book he said that he went for a walk and decided to sit down and "read a newspaper in the shade of the bank," after which he decided to get some lunch. 100% of readers would assume he meant that he sat down and read a newspaper in the shade of his local banking establishment and that he had used "bank" with the same meaning all 1,000 times, assuming there was a nice bench out front of the bank, or maybe a nice little cafe that happened to be positioned in the shade of the bank during the late morning hours. Readers would assume this because it is the only reasonable way to interpret the statement within the context of the book. Every other time it is used it means his banking establishment, and in this instance there is nothing that shows the author obviously means something else, like the river bank. And heaven help this author if the fact that the newspaper was read on the river bank rather than in front of his banking establishment is in any way important to the story, because nobody is going to have any clue. Trying to convey this event as happening on the river bank in this way, using "bank" in this kind of sentence after its consistent use to refer to a local banking establishment, would be communicatively nonsensical. This type of incompetent writing would make for a very short career.
Likewise, it would be communicatively nonsensical for John to attempt to convey the idea that Jesus is the source of the creation by God rather than the first part of it by using a word that he uses everywhere else to mean a partitive beginning; unless he used it in a sentence where it obviously could not hold its usual meaning. But just the opposite is the case. He used it in a sentence that actually strengthens the likeliness of it holding its usual meaning. As such, nobody could reasonably be expected to take such a different meaning from his words. That Trinitarians do take a different meaning is not a counter-argument, because they do not take a different meaning as a natural function of the language. They just don't. The meaning that they take is specifically intended as a preferred alternative to the obvious reading. It might be technically possible if you just grab those words and randomly put them on a blank page, but it is not a reasonable reading of John's words at all, unless we take John himself to be a most incompetent author who does not communicate with his audience in a reasonable manner, in which case it's not the reading that's made reasonable but the author who is made unreasonable. There is a certain gnostic quality to this kind of reading.
If John wanted to convey the message they would like, it is only reasonable to expect that he would have either used the word in such a way that it was obvious that he intended a different meaning than 1) his usual meaning and 2) the default or unmarked meaning. Preferably (from a communicative perspective), he would have used a word that more directly carried his intended meaning in common usage and was unlikely to be misunderstood in the context of his writings. He did neither. As a result, there is precisely one reasonable interpretation of his words.
On a related but different point, Sulla made an interesting comment about Thayer's applying a meaning of source to arche in this verse, asking if it was Unitarian bias that motivated this reading. I would actually say this is entirely possible. As has been discussed at length, Thayer's cites as examples of its meaning of "source" cases where arche is used to indicate a partitive source. As a Unitarian, this is kind of perfect. It identifies Christ as the first creation that carried out the rest of creation; the first instance, which is the efficient (rather than formal) cause of all the other instances. As a Unitarian, I'd be very happy with this meaning too, because I think it accurately conveys the truth about Christ. However, I would not accept it as being a truly reasonable reading of John's words, no matter how much I like it. It's certainly less problematic than the meaning Trinitarians prefer, because it adds another layer ON TOP of the meaning he associates with the word everywhere else rather than DIVORCING the word from its meaning everywhere else, but it isn't really a reasonable reading. There is no basis in the context of John's use of language (or the language of the NT) to think that's what he intended to say there. There is really only one reasonable meaning there if we're going to read John the way we would read any other author according to the basic communicative logic that is employed in both speech and writing.