Transferred to military school and repeated 11th grade because he was really young for his class. Now he is just on the older side of his class. Not a fatal strike because obviously there are lots of 19-year-old JC players that can be good picks.
I think this was just something people found in HS rankings that when the player was a little old for his class the outcomes relative to draft position were a bit worse. MLB could be sophisticated enough to account for this. Remember this was a strike against Blake Rutherford a few years ago.