Perhaps I should explain what I mean a bit better, I typed that in a hurry.
CPUs can deliver a certain number of frames in a game. GPUs can deliver a certain number of frames at a particular setting in a game. However, CPUs don't affect how many frames a GPU can deliver or vice versa, you simply get whichever is lower. Either one or the other will be less than 100% utilized in every case.
A faster GPU will allow for either 1) higher graphical settings at the same framerate, or 2) higher framerates at the same graphical settings, assuming you haven't hit the cap your CPU is able to deliver. I consider it a meaningless question because "bottlenecks" are moving targets, you can change which is bottlenecking the other by changing...