Here's a Finder window screenshot from Mac OS X 10.0 Cheetah: https://512pixels.net/wp-content/uploads/2018/08/10-0-Cheeta...

Notice two things:

1) The window chrome with traffic lights and title is entirely separate from the toolbar, not unified with the toolbar.

2) The top of the window is rounded, but the bottom of the window is not!

I think the old design was superior for several reasons, one of which is that it made the windows much easier to drag around the screen. In any case, though, even if there's an argument about concentricity and window controls, it makes no sense that the bottom of the window has the same corner radius as the top when the toolbar is only at the top.

IIRC, you could even "roll up" the window into the top window chrome, with that transparent pill button on the right.