Describing reality accurately is not an appeal to anything, except maybe common sense.
There is a logical fallacy called "Appeal to Common Sense" too. Obviously what is common sense to you may not be common sense to anyone else.
Common sense is the same common sense for everyone. That's where the 'common' bit comes in.
For instance, some developers keep a development diary letting fans know what features they can look forward to. It boils down to making development less of a black box and engaging your audience in a way that piques their interest.
Larian has done this frequently with their games
. In fact, they even posted 52 updates and 16 FAQ entries about it. So I'm not sure entirely what your argument is; Should Larian already have a full feature-creep list of everything planned for BG3, including a tidied out roadmap about the whole process this early in the process?
Even then, please refer to any single academic or legal source online that makes this a fact beyond opinion, that claims marketing should work a certain way in which you're implying (Of which, to be perfectly honest, I have a hard time understanding the logic of. Sorry!)
I'm personally extremely hyped about Halo Infinite, but I'm not pissing myself over not knowing everything about what that game entails. And that's a year away from release, way less time than BG3.