Chef, first off, let me say I am sorry for your son's injury. I'm not a orthopeadic doc, but I will tell you where I stand, having the ability to look back on my son's situation. My son felt a "pop" during a throw from the outfield when he was 15. We had x-rays, MRI and examination which all revealed a UCL tear. Son had no pain, even during docs exams. Our local ortho referred us to Dr. James Andrews. Son saw Dr. Andrews about a month after the injury. During his examination, I could see the look of confusion on doc's face as he was expecting son to exhibit some pain, but to his surprise, my son complained of zero pain on all the movements. Dr. Andrews was great! He took a LOT of time talking to us and explaining his findings and recommendations. He suggested that we proceed with rehab, but he warned me that surgery may still be required in the future if he didn't respond favorably to the rehab.
Son did the prescribed rehab and followed up with Dr. Andrews 6-8 weeks later. A second MRI was taken and showed his UCL scared over and healing. Dr. Andrews was certain he would make a full recovery and released him to normal playing about 4 months later.
Fast forward 3 years. Son feels a "sensation" in his elbow the morning following a complete game in which he threw only 89 pitches over 7 innings. The team trainer felt like it was just soreness and nothing structurally wrong. After 2 weeks of rest, the issue was still present, so we saw the ortho doc once again. This was a different doctor from our first visit. On examination, he felt certain there was no structural damage. The doc didn't want to do a MRI. I basically demanded it as son was getting a lot of pro interest leading into the 2015 MLB draft. The MRI showed no structural damage, and the ortho told me his ligament looked better than it did on the MRI from 3 years prior. We talked with his HS coach and college pitching coach and all agreed to shut him down as a precaution until he got to campus for summer. Son went through the summer throwing program with no issues while throwing long toss or flat ground. When he threw his first bullpen from the mound, he felt the "sensation" again. The trainer immediately diagnosed it as an ulnar nerve issue and he was referred to the team ortho. On his examination a few days later, he confirmed the trainer's diagnosis and set son up to have a nerve conduction test. The test confirmed the clinical diagnosis, and son had ulnar nerve transposition surgery in August. He rehabbed from the surgery and everything progressed seemingly flawless. Son was again able to throw long toss and flat ground with no pain or issues. His first bullpen from the mound, he felt a "pop" on his 4th pitch. A UCL tear was feared and that was confirmed by MRI a couple days later. Son had UCL reconstruction December 16.
I know this has been a very long post, but I'm trying to lay the groundwork for my opinion. With all the information I have now, I still do not know if I would have done anything different. You can really only go by what the experts recommend. I do think the original tear of son's UCL never completely healed. He does have a slight mechanical flaw where he throws from a slightly closed position. Other than that, I have never had anyone tell me that son had mechanical issues. He has never had a pitching lesson, but he has thrown in front of many, many scouts. I would think that if a major flaw was present, someone would have said something by now.
I think your son is a freshman or sophomore in college, right? My opinion would be to lean toward the more aggressive surgical option at this point I think. Maybe being conservative is the right call for a young teenager, but at this point in your son's career, I would rather have the issue solved rather than putting a band aid on it, per se. Again, I'm not an ortho doc, but I am in the medical field and have a fair amount of knowledge and understanding of anatomy. Everyone is different and each has his own opinion. I'm just giving you my opinion as my son is 2 months post-op. I'm not saying we or he would have done anything different. It is very difficult and I really feel for you and your son.
Things happen for a reason and I fully believe that God is in control. My faith is the one thing that I can hold on to. I can tell you it is very difficult to see my son sitting in the dugout watching his teammates perform and knowing he can't. This is the first time he has missed any sport due to injury. I have to believe God is teaching him something. Hopefully we are able to look back in a few years and see the lessons.