Thanks for the of the responses, experience and advice. I really do appreciate all of it.
My 12u 6th grade son's diagnosis is in fact Medial epicondylitis (ME) with advice to rest until the spring and do some PT. The condition is not the same as "little league elbow" which has more to do with the elbow. He does not have separation at growth plate either which is good but we need to have further tests later to ensure this does not occur. Now that he has stopped throwing altogether, I think we can avoid this.
I frequent this site because I have 2 other boys one a 2020 and also a 2023 (12u) that have bright futures in baseball. The boy who got injured, ironically, is not the one who pitches 100 innings a summer. He does catch but that is pretty limited.
His career in baseball will likely be playing HS ball and competitive travel ball but we are not concerned about college ball for him at this point because he has never expressed the interest or ability to play beyond school ball. So the advice that is important to me is not that someone's D1 son had this when they were 12 ( with a growth plate issue) and proved all the doctor's wrong by not getting TJ surgery, but how quickly someone with ME got back to playing youth ball (we have Cooperstown this year and if that's not a good idea I will need to make some decisions).
By the way, 75% of what I read about this diagnosis has to do with tennis. I don't think it's a coincidence that we (my wife actually) put him on the club tennis team and they were out playing 2-3 days a week as well as playing golf twice a week during the spring and summer. In fact his youth team (a USSSA Major level team) stopped playing in June because their coach had to go coach another team. So I think this is due to the other sports just really interested in experiences with ME in a young player and the road to recover. We will follow the Dr's advice, stop throwing until the spring, do the PT and see where he is.