My son has this problem and in fact is still going through physical therapy for strain to the cuff. As it was described by the doctor loose joint syndrome is hereditary, however the therapist and the doctor both said they see this with good pitchers(high velocity).
Per both my son will have to do these excercises to strengthen the shoulder as long as he is in athletics.
By the way his injury came about in football. I was pleased when he told me football can go to the side as baseball is more important.