The scroll thumbs actually have about the same area as the scrollbar. Maybe larger, because the little tab pops up under wherever the mouse is, so you don't need to seek for it vertically like with a normal scrollbar. In theory.

In practice, they're too fiddly, sometimes appearing on the inside, sometimes on the outside, and requiring you to move your mouse in and out of the window frame. If they get that sorted, they'll be on par with (if not better than) normal scrollbars, imho.