Anyone who has ever worked with an instructor to get his golf swing fixed knows how you go through a period where your swing gets worse, and your whole game falls apart. At some point you'll be convinced you're wasting your time and your money.
Phillips played like a great, young athlete with a head full of new-but-not-yet-absorbed knowledge in his head. In the process of trying to learn the new things the coaches were teaching, and stepping up in competition without the benefit of a corresponding step up in his physical body, it's predictable that a 5-star would get discouraged.
It's probably a place his head has never been before.
We've heard many stories of athletes who got discouraged and wanted to go home, but a strong parent kept him here and wouldn't let him walk away defeated.
But what happens if there are dissenting voices coming from family? I have no idea if any of this is the case here...
but all this is far more logical than assuming that Phillips is not a very good basketball player, or that Barnes destroys offensive skillsets, while being unable to coach certain positions. Every person and every situation is unique.