Focus follows mouse was a thing in the X11 era too. We are still in the X11 era, and it is still a thing. (-: Until X11 window managers like IceWM vanish entirely, it will remain a thing.
replyI think of focus-follows-mouse as a different thing. FFM raises the window under the mouse, but doesn’t move the text insertion point (at least on X and Windows, the only two places I can remember using it). But the Apollo’s window manager was different - moving the mouse moved the insertion point along with it.
replybut raising the window under the mouse also, for "true" FFM, gives kbd focus to the raised window, which will in turn (via whatever GUI toolkit is being used) moved kbd focus to some widget in the window, if possible.
replyIt is impossible to generalize about this under X Window, since the behavior is entirely controlled by the window manager, and their behavior (a) varies (b) is very customizable.