Huh. I wonder why they thought this was such a big deal. I mean... the user caused the problem, and could easily fix it by enlarging the window. Other windowing GUIs handle this just fine.
There are, of course, ways to indicate "more controls this way" with an arrow or other affordance when there's a toolbar or menu overflow, though.
Anyway, the point is that by the time OS X came along, other platforms had solved the problems but Apple rejected those widely-accepted solutions.