The key distinction there is that there is a visual element that does still respond to taps/clicks, which means that eventually you try to click on it, overshoot to the corner, and discover that you don't need to click at all.
Gnome shell does some of this stuff well, but try using it for real work on a tablet and you start needing those arbitrary gestures again. Need to invoke the on screen keyboard? View the app overview? You're going to be searching the web for those gestures, guaranteed.
