"Categorically distinct" is not, I think, a useful term here. When I use a term like "simulation" in referring to a game, I'm referring to its primary intent and apparent design. As I've noted, it is very difficult (and questionably desirable) for a game to be all the way over on one axis. But you can look at what a game is doing, and apparently trying to do. And that can still convey useful information.
What it can't do, is present a value judgment, except from the perspective of people who consider simulationist/dramatist/gamist to be values by themselves (which there are absolutely people who do, but the very first development of these terms in an RPG was by people trying to make a point that there was value in all three (even if a good part of them treated gamist like the red-headed stepchild), just to different people to different degree). Edit: I know you've indicated this is not your issue here, but I do think its been an undertone of some responses in this thread.
I honestly think a good part of resistance on this question is either from people who (for whatever reason) really want D&D to be able to wear the hat of "simulation" whether it seems to fit or not, or who consider other people saying it doesn't as doing so as a backdoor criticism of it (even though there have been multiple people in this thread who made it clear that they don't consider that particularly a criticism).
(As I've noted, fairly few modern games are particularly simulationist, in part because a preference in that direction has never been that common and shrank over time (I'd speculate it correlates slightly to the diminished percentage of heavy wargamers in the hobby compared to early on. One could question that by noting that the strongest presence of simulation-heavy games took about five or so years to start to land, but I think that had to do with the relatively minimalist tendency of most of the earliest RPGs), so that there's simply not that much of a market for it as compared to the other two wings and combinations thereof).
By your definition, can any game simulate a fictional universe? Or can simulation only be for the real world?