I had several coaches mention this to me over the years, and seen it play out a few times as well. It takes some players a year or two for things to click. It's not that they're not making the effort, or being difficult. For whatever reason, some of the concepts that a coach is teaching, that need to be automatic and instinctive, aren't.
Was just talking last week with a guy who coached for many years at U. C. Davis in Ca. Was part of their Division 2 National Championship team. He said his experience was that it generally takes a player out of high school at least a full season, sometimes 2, to fully comprehend what it takes to truly be consistent and competitive at the college level. We talked about a local player that should be dominant athletically. In a straight up man to man, she can guard anybody. But as soon as you get into different scenarios on when to go over/under screens, who and when to switch depending on the current situation or individual match-up (we all know those rules can vary during the course of a game or even possession) she gets a little lost. She knows what do to, but it takes her a second to remember sometimes. It's not always an instinctive reaction for her. Since her coach sees in practice that she sometimes struggles with that, and he doesn't know for sure how she'll react when the situation comes up in a game, she doesn't play.
Sometimes for a player, it's like the fundamentals of algebra either clicking in or not. Some players get it right away, some players take a little time and some players never get it. It's hard to give up on a guy when you see them physically and think "If it ever clicks for him, he could dominate". I think JOJ might be in that situation. As for demeanor on the bench, sometimes frustration with yourself can look like discontent. I haven't watched enough to notice, but a player also needs to realize that body language matters whether you think so or not, coaches are paying attention.
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