It's probably stuff in the general category of 'giving more detail would itself be spoiling what's coming, so they have to be vague'. Kinda like how, if you spoiler-warning all the side content relevant to the Ascians, the fact that Eden is on that list would itself spoil Eden. (Incidentally, if anyone has a good term for that, I'm in need of one for my videos, I bump into those a lot.)

Like, consider that we now know that the all-roles capstone questline is going to be in Garlemald, but we know nothing else about it. If they were specific about saying that we were going to learn more about, say, Nerva, then suddenly we know exactly what that one questline we know of that's going to Garlemald is going to be focused on.