He's strong but does look undersized and unfortunately doesn't have a freakish wing span to make up for it. I agree that if he were 6'9" or 6'10" he's probably a top five pick for sure. This said, his two best skills to me look like:
1) His general BBIQ, overall skill set and understanding of how to play the game
2) Perhaps most importantly he really understands how to use his body and his strength, in small spaces, to A) Create space to get his shot off and B) create contact for and ones as he has the strength to finish through contact
I'm liking the pick a bit more the more I see of him and the more I listen to him talk. Super bright kid.
He may not be our long term starter at PF in time, but I'd be surprised if he didn't turn into a solid long term rotation/role player guy for many years