The mental overhead from having slightly different drop shadows and button sizes is minimal, and I think pretty overblown by people who prefer identical UIs for everything regardless of form factor (which is of course a valid take).

But someone could just as easily respond to today's UIs with "Yes, it's wonderful that every single app looks identical, as if it was all designed by one pretty boring artist with no creativity whatsoever" and that would also be a perfectly valid take.

Predictability is a feature. That does include button sizes. To me that's where the asymmetry is. The "boring artist with no creativity" complaint is aesthetic, whereas predictability is a functional concern.