None of this has to do with consistency, though, which is the topic at hand.
I mean, maybe you can say Windows has "one window system". But Microsoft has over a dozen GUI frameworks, and then they don't even use them. Teams is electron, believe it or not. I mean, in windows TODAY you can find UIs from 1995 to today in there.
And that's just Microsoft software! The pre installed shit. Don't even get me started on applications. Let me tell you, that's not a problem on KDE or GNOME.