Zelda also has nothing to do with it.
What I mean is that they're big games, with a lot of variables and optimizations. Conventionally Baldur's Gate will perhaps sell better if released by the end of the year than if it was released now, and the extra polish might create better initial sales.
But that's just me, as you say I was looking at the bright side of things, I like big games to come out in a mature state, and hope that's the case for Baldur's Gate 3, I'm thinking this stupid Xbox Series S conundrum with a feature they could either skip or implement later is... quite idiotic, but if the game could benefit from a bit of extra polish across all platforms then it's also an opportunity.
I doubt optimizing for Xbox Series S is all they're doing in this time, that was all I was saying.