I hope he worked out to some extent. The more I've read about his knee injury, the more I'm inclined to speculate that he has a torn meniscus. May be minor, but would seem to make the most sense given the extended rest, WU's secrecy about it, and the repeatedly swelling often associated. Hopefully there's nothing structurally wrong, or serious in general.
Could just as easily be a player/coach being supremely cautious with a top prospect. Let's be real -- these recent top prospects (e.g., Simmons, Fultz) are attending middling college programs for 6 months in order to demonstrate their next-level talent and not get injured. Nothing more, nothing less. Interesting situation.