Do you get the feeling that he plays small? Whenever i watched him I just always thought he was 6'3-ish. That is one of the things that bothers me about him, though it may just be in my head.
I don't. Not at all.
Here's what I think you're seeing (just a guess). Some small (6'3) guys play on teams that lack bigs and they muscle and hustle down low for rebounds, putbacks, etc. Makes them seem like they play bigger than they are. Then there's Darius. He has played on a team that features truly elite rebounders, shot-blockers, athletes .. and he happens to be a 45% perimeter shooter. UK needed Darius, with his shooting touch to play on the perimeter (like a 2/3) and use his length and athleticism (best athlete at UK) on defense there as well. This can make a guy seem to play smaller than the guy that's gutting it out in the post.
I appreciate your sincere question, btw.