dtgreene: If this does happen, it will be obvious that something happened and you can just not save.
Gotcha: Just tried it: You can still save since you'll wake up at the shelter as usual anyway. But if you encounter this room the world will be in 'armageddon'-mode, e.g. everyone except for you and LB will be dead.
Yes, you can save, but you don't have to save, and because it's obvious that something is wrong (unlike the case of flying of the Isle of the Avatar), you can choose not to save.
Also, I note that Batlin will be there (and will say what he normally does post-Armageddon), as will the ferryman who takes you to ruined (again) Skara Brae. (How many times has this town been destroyed in classic CRPGs? There's this game, one of the other Ultimas, and Bard's Tale 3, all which had a town with that name in ruins.)
As I said, however, I strongly suggest talking to Lord British a few times after being accused of cheating. He does not say the same thing he says post-Armageddon.