Can't one say, for example, that the laws of presumption are factual? Meaning: in order to bring about something-or-other that existed in the reality of that time, or that depended on the reality of that time, which is no longer the case today.

Not only can one say that, one can't say otherwise. What does that have to do with the discussion here? Presumptions are factual determinations. But the question was whether the Sages made only determinations of that kind, and the answer is no.

I think he's asking whether the determination that "presumptions can extract money" (the laws of presumptions, not the presumptions themselves) is factual. That resolves a few difficulties in his wording.

Better to force the wording than the logic. If that's what he means, then it's really nonsense. That's a purely normative determination. What does it have to do with factual determinations? Is the prohibition against eating pork also, in your eyes / his eyes, a factual determination?

In my view, no. But why is it nonsense? Couldn't there be "halakhic facts" from which norms are derived? Something like essentialism. (You'll probably say that the Sages can change facts of this kind and that it's uninteresting semantics.)

Unfortunately, I don't read Chinese. 🙂
How is the determination that a presumption can extract money different from the prohibition against eating pork? How can one view claims like these as facts? If you call norms "halakhic facts" (in the sense that I use the term "ethical facts"), then fine — but what have we gained? There is still a statement here that does not depend on circumstances.

What prevents us from saying that the prohibition against eating pork (let's ignore for a moment that it's Torah-level / of biblical origin) is a factual determination? Or alternatively, a determination of a norm that is based on some moral norms / scientific views / social conceptions that existed in their time and whose validity has now lapsed.

As stated, the first is nonsense. And of course there's no obstacle to the alternative. But even when you propose such an alternative, you still have to explain what the factual basis is and what changed. And once you propose it, you'll see that a norm is hidden there too. You can never derive a normative conclusion from a factual premise (that's the naturalistic fallacy). The bridging principle that connects the two planes will be the binding norm.
For example, if you explain that the prohibition against pork stemmed from the fact that pork is unhealthy, and today our nature has changed and it has become clear that it is healthy, that is in principle a viable possibility. But the norm would still remain that unhealthy food is forbidden to eat. And that is not subject to change (because of the authority of the Torah or the Talmud).

If so, what's the problem with saying that the norm remains but its application, כביכול, has been nullified? That is, that it is forbidden to eat something unhealthy, and pork is no longer unhealthy, and therefore today it is permitted to eat pork.

Who said there's a problem? That's exactly what I wrote. This whole discussion seems bizarre to me. I wrote things that seem completely clear and simple to me, and I don't understand what's unclear.