Comment by ireflect

> double clicking the Finder titlebar only expands it vertically while every other app expands both vertically and horizontally

For me it fits-to-content both vertically and horizontally. I just tested in both list- and icon-view. Mac OS 12.

> When I close a window and then press Cmd+tab, the icon is still there

This is because the Mac UI application/document conceptual model, which has been consistent since at least the 1980s. An application is either open or not. If you have multiple documents open, they are open within a single instance of the application. You can also have zero documents open. The application doesn't quit automatically when you close the last document.

Other operating systems flatten these two concepts into one, such that each new document appears as a new instance of the application.

I'm not suggesting one is better than the other. Just that I don't consider this a lack-of-finesse since it's been my mental model for 25+ years.

I'm also not disagreeing with your overall point. I can think of plenty of inconsistencies and lack-of-finesse in modern Mac OS UI, to be sure!