Actually he averages closer to 9 (8.8) rpg. But even that doesn't tell the whole story. He does that in only 20.9 mpg. By comparison, Oscar was averaging 14.3 & 12.2 rpg playing 31.9 & 33.5 mpg. So how does Williams rebounding compare to past UK players this century?
First of all, you have to standardize the rebounds, so making an even comparison, so below are the best 8 per30min rebounding averages for a season at UK this century:
14.3 Oscar
13.9 Vanderbilt
12.6 Cousins
12.6 Williams
12.2 Oscar
10.1 Randle
10.1 Humphries
9.7 Davis
Maybe he relies on his height, reach, athleticism to rebound. The opposite of Oscar. So what, he gets them, better than most.