There's also the problem that not every window in Tahoe has the same corner radius. Some people thought this was laziness/lack of polish or a bug, but Alan Dye confirmed on a podcast that it was intentional.

So then they're left with a conundrum: do they adjust the 19x19 region on a per-window basis, depending on the per-window corner radius, or do they stick with one standard drag region? Probably it should be the former, but that comes with its own set of issues.