[NoOne]

The fact that he retained his potential rating from 16 to 21-23 is a good sign. Usually if this is a false value, it becomes apparent after a few years with scouting and mil experience under their belt. That is not the only way to fizzle out (false ratings from bad scouting) Sometimes they just don't develop, and if it continues into age 24-25-26 you give up, because they aren't getting any better (current ratings). 24 is possible but the chances are dwindling fast. If i had to guess 26 is the cutoff but if they finally blossom, it's rare at 24+.

Those highly rated 16 year olds are even less likely to be true than the highly rated 18 year olds in a draft by a wide margin, and the draft is low-probability to start, lol. Keep the faith, but expect more than a few failures.

Bad stats are okay as long as the current ratings are developing and not overmatched for the level. Stats wwill always lag behind ratings, and more so with faster re-scouting increments.

All that matters in the MiL is development. If he's developing super fast and hitting .170, that's fine. If he weren't supposed to be at that level, his ability wouldn't be sky-rocketing. You develop better at each successive level, including ML being the best dev - either due to rate or lack of soft-ceiling. If rated well enoug for the next level, they should be promoted regardless of stats.