I wonder if this is designed by primarily laptop users. They may conceivably prefer buttons at the top because it’s closer to the center of their field of view.
Of course, laptops used with their builtin display and keyboard are a usability disaster already, so that shouldn’t be a criterion.
For what it worth, gnome is very good to use with a trackpad, swiping left-right to switch between desktops is very smooth, probably the best laptop experience out of any OS/DE.
Of course, laptops used with their builtin display and keyboard are a usability disaster already, so that shouldn’t be a criterion.