As an aside: It is reasonable to guess that extreme use of his arm at that stage of life could be responsible for the pitching arm vascular irregularity as well.
40% of all pitchers have Tommy John surgery at some point, though I get that being younger could be worse over the long haul. Then again, it wasn’t a surprise when he was acquired.
Having TJ that young is an issue though. It suggests extreme usage of the arm at a young age when the structures of the arm and the body as a whole is still in the growth stage. It is now known, or highly suspected, by legit sources, that such extreme use can cause abnormal development. In at least one case I have looked into this abnormal development was shown to result in shoulder architecture which places the arm in a disadvantageous position for tolerating stress without injury. I have previously posted a link to that study.
I get it bling, but there are examples of successes, too. A quick Google search indicates that Lucas Giolito, Max Fried and Dylan Cease are among current successful MLB pitchers who had TJS as a teen.