Footwork is the key to acquiring and improving good post moves. Haven't had the opportunity to catch Nwoko's footwork but I would hope/expect that was part of evaluating him. As you say, boxing out and rebounding would be a great start.Rebounding is more want to than anything. I can teach a 7 footer that has a good work ethic to box out. What I can’t do and apparently L and his staff can’t do either, is teach post moves on the offensive side.
As for 7 footers (which Nwoko is not), the list of players at that height in college who never amounted to anything is, I'm sure, well into the hundreds.