Annoyingly it doesn't even maximize properly. You have to use alt-click for sensible behaviour.

They also decided about 10? years ago to make it behave as a "fullscreen" button which was really useless to me on a Mac Pro with 2 screens, where it would only ever "zoom" to one screen and then make the other screen display the desktop wallpaper - not the actual desktop - the wallpaper.

Useless.