This stuff about his defense may end up being spot-on. But I think something might be missing with people who did not watch his entire college career and put it within the context of the UD team.
As I watched his career at UD progress, and knowing the depth chart at UD and his value to the team, I felt that Obi was being coached to be inert when his man had him out-positioned around the hoop. I felt he would offer up just enough resistance that he would very rarely be called for a defensive foul. I thought that it was a strategic team decision on the part of the coaching staff, and not a lack of Obi's ability on defense. There were a ton of plays where he could have gone for a block, but at great risk to picking up a foul. I thought it was self-discipline and good strategic coaching that held him back.
I don't know if that assumption is true, but I think it is very possible.
I guess we will find out when he hits the NBA.