> the fact there are two pointers on the screen -- one for the mouse and one for the keyboard -- if you slide the mouse pointer to a specific point and press a keyboard key, the new key will not appear where the arrow is, it will appear where the text cursor is.
I remember using an (early?) Apollo computer that worked that way... I was warned by the person showing me, and a bit later he accidentally bumped the mouse while I was typing! Letters all over...
I believe this was in the era before X windows took off for unix boxes. I miss SunTools - it was nice and simple.
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.
* https://ice-wm.org/manual/#focus-models
I 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.