Mr. f: I screwed one of my 9/32 shafts onto one of those points apparently chamfered to 5/16. Actually, the difference is so small as to be almost unnoticeable, at least I didn't notice it, and certainly inconsequential.
The difference between 9/32 and 5/16 is 1/32. On the outside diameter, that amounts to 1/64 of an inch on a side, so to speak. Difficult to detect with the naked eye, and, given the chamfering that's on the rear of the head, not enough to impede pulling the arrows. I guess what I'm saying is that chamfering to 9/32 instead of 5/16 would have little effect.
The larger diameter of the rest of the head does impede pulling, but the chamfer helps ease it some. I think I prefer it to a point that would need to be another half to one inch longer at 9/32s.