My son went through a period of shoulder pain several years ago. I'll share some thoughts to help give you perspective, and maybe some follow-up questions to ask your ortho.
My son had a very similar experience to your son. He was playing in a USA tournament and played something like 8 games in 6 days in 110+ heat in AZ. In the last game he felt a sharp pain in his shoulder. We took him immediately to an ortho who gave him a battery of tests and x-ray and declared his shoulder structurally ok. The recommendation was that it was overuse in extreme heat and he should rest. This didn't sit well with me so we found another ortho... basically the same diagnosis, but with a recommendation to go to physical therapy. It turned out my son's shoulder was extremely tight with very limited range of motion. He went to PT and got stretched out and improved his range of motion. He could rest for a couple weeks and be ok, but then it would flare up again. This went on for many months, perhaps a year. Each time I feared the worst and worried about a labrum tear, and deep down I wondered if the orthos were missing something really bad.
The pain, it turned out, was bicep tendonitis from friction in the shoulder when it wasn't extremely flexible. We found a new PT who figured out how to stretch his shoulder so the capsule inside could be properly stretched. Once he figured this out his shoulder never had a problem again. This guy was more helpful and seemed to know more about shoulders than the orthos.