Professional sports teams with multi-million dollar athletes don't settle for lousy medical care. And University of Pennsylvania with their first rate medical specialists is right there. And if that's not enough, teams routinely fly athletes to whatever specialists are felt to be necessary, regardless of where they reside.
This is not incompetent or lazy doctors. This is a player who's been looked at from every angle, imaged and tested extensively, and no one was able to come up with a definitive diagnosis. Thoracic outlet syndrome, since most of the time there's no objective testing for it, is the kind of diagnosis someone may get when nothing else turns up, and the doctor is reluctant to suggest a psychological issue. It might well be that the Fultz team shopped around until they found someone willing to give him a medical sounding diagnosis.
Regardless, it's time to stop rehashing this. I'm very hopeful that with a much less stressful environment, much lower expectations, a better fit with teammates who won't hog the ball, and basically a new start, that whatever the problem was, it will improve.