No, whenever I start a save in a world other than Forgotten Hollow, absolutely no vampire townies spawn. The only way I can get vampire townies to spawn is by either visiting Forgotten Hollow or playing there.
I might have to do some testing again. Maybe this was fixed in a recent patch?
I've never had a problem with vampires not spawning anywhere but Forgotten Hollow though. I play the most in Willow Creek and I think all of the homeless vampires in my game now were probably generated while I was playing there. And I've definitely never had a problem with aliens in disguise not spawning and I never play aliens, so any aliens in my game are generated by the game and not me.
Have you tried testing a completely new save that's never seen mods? Might even reset your Sims 4 folder just to be on the safe side too.
