He's improving, this is what he looked like a couple of months ago -
Jahlil Okafor #2 Prospect in 2014 according to Scout.com - Spring/Summer 2011 Highlights - YouTube
He could barely dunk, lost a lot of weight and is becoming more explosive. What I see is a kid that is comfortable playing with his back to the basket, and already has a decent set of moves. When looking at HS bigs you really only compare them to one another, and his post game is advanced by HS standards.
He's probably 6"10 and change, when he dunks he doesn't need to take a drop step on some of them, which you never see from someone like Sullinger who is 6"9.