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.
It’s more like I have to actually think about where the program options are. Or that on firefox nowadays I have to snipe a tiny small spot on the title bar to move the window, instead of clicking some button that doesn’t look like one.
When I first used MacOS I was surprised about tute consistency to access the settings of every program, even third party, with the same shortcut cmd+,
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.