access to desktop has been critical in the past, and even current intel 10.4 system.
being able to touch the desktop with the cursor allows you to get control of a functional cursor if yr app is acting up and you get the Spinning Rainbow Beach Ball of Life.
have Safari open and maximized to the extent that it is up against the top system menu bar and the left edge of the screen. that little tiny rounded application curve is there for a purpose: position the cursor just right and you can touch the desktop and access finder.
rounded edges are there for more than to be different. they were needed.
That little tiny rounded application curve is still there. Take a look at the attached capture. The menubar is what has lost its curve, not the application. And clicking in the curve-void of the menubar is the same as clicking the menu bar itself - so no functional change.
Your scenario still works... though I've never needed it.