@daringfireball “by 2011 it had long been the case that users could resize windows in two dimensions starting from any corner, or in one dimension starting from any edge of the window.”
Lion was actually the first version of Mac OS X that allowed resizing from any side of a window. Previously, windows could only be resized from the grippy-strip.
I think they dropped the affordance to not imply that resizing could still only happen from that corner.
I also think it was wrong-headed to drop it.