-1
Since window border and the sizegrip are set in two different windows, disabling the sizegrip by default makes it completely undiscoverable.

Also, though I agree that you can resize the windows from the borderless borders,
1/ as far as I remember this is true only when compositing is on (and maybe, always on wayland; did not check. In fact it is probably completly broken on wayland atm).
2/ the hit area is much larger than the out-of-window borders; and the area is always visible.
So that (for me at least), is is much easier to resize from this handle than from the invisible borders.