Yet it survived in tact, more or less, with key details ultimately true. Is that more realistic or less, I dunno. 200-600k years is a long time.
You're confusing two different things, the Admonition itself and the Romulans' legend of the apocalypse. Just because the Romulans later equated the two doesn't mean they had the same origin. Again, it is a profound, fundamental mistake to assume that the way a present-day culture tells the story of its past must be literally factual. Cultures reinvent their pasts all the time. Even things from as recent as 2-300 years ago are distorted and mythologized (George Washington didn't have wooden teeth or chop down a cherry tree as a boy), let alone ten or a thousand times that long.
Mistake or not, it’s there now. I’m just trying to figure a way to make it fit.
The way to make it fit is
it's a mistake. Simple as that. Anything else is unnecessary. All you have to do is be willing to believe that fictional characters are every bit as fallible as real people -- or that the creators of fiction sometimes goof up and let a mistake slip through.
Unreliable narrator, sure. But then who’s to say anything we’ve seen or heard in Trek is true? You can get really solipsistic going down that route, and I don’t think that’s as interesting here.
That kind of blanket generalization makes no sense. It's a matter of assessing each
individual claim on its own merits. This specific claim contradicts everything we've previously known, it has zero corroboration by any other data point, and it's spoken by a known liar belonging to a fanatical cult in an authoritarian state, not to mention desperate, exhausted, afraid for his life, and perhaps not thinking entirely clearly. All of that makes it easy to dismiss. That has absolutely nothing to do with the credibility of any other claim, because each case is different.
^ I think he’s saying that they were called Romulans initially until the Surakians renamed themselves Vulcans? They weren’t, as far as we know, but that’s an imaginative suggestion.
Despite that idiotic moment in ENT: "Minefield," they were never meant to call
themselves Romulans. The obvious intent in "Balance of Terror" was that it was
humans who named their "twin planets" Romulus and Remus after the twins from Roman mythology, and then devised the name "Romulan" based on that. It stood to reason that their name for themselves was different (which was why Diane Duane's novels dubbed them Rihannsu).
For that matter, "Vulcan(ian)" was probably meant to be humans' name for them rather than their own, since it's also a name from Roman mythology.
In any case, it's impossible that the Vulcans originally called themselves Romulans, because then that would've been part of the historical record, and thus it wouldn't have been a surprise in "Balance of Terror" that the Romulans were related to the Vulcans. The connection had to be unknown until then.