The stat cast average ev is irrelevant because peaches grandson isn't facing 90mph sliders. 15u pitching has far less variables, and thus the average exit velo will be much closer to max. No matter what stat cast measurement your sort by, there is almost no correlation with top players. Guys who hit 35 home runs have ev 10 points lower than AAAA players. You might not have read my post; I refer to stat cast data several times. I simply deduced ev off a tee by subtracting the help of the pitch from the max reading on stat cast. You also make a key miscalculation in saying the average ev is 20 mph below their max. The ball is going to add 13ish ev, so a 110 on stat cast is a 97 on a tee, meaning an average of 90 is only 7 mph, not 20+ below their best. If exit velo from a tee didn't matter to someone, then no one would measure it. It's like the vertical jump in football, raw power output.
My point is it doesn't matter how you measure exit velocity, and it doesn't matter whether the players are MLB. You are choosing to ignore the trend based on the level the trend is measured at. I think the trend is probably true at any level. The facts are that the players are facing typically similarly talented competition. 15U players face 15U pitching, MLB caliber players face MLB caliber pitching. 15U hitters have 15U experience and strength...MLB players have...well..you know.
Sso to say that the difference in average exit velo versus maximum is more because they are facing better pitchers doesn't wash with me. Why would you deduce an exit velocity when it doesn't matter what it is off a tee? If it was something that mattered maybe MLB would produce those numbers. But what matters is what you do in a game, during live pitching...last time I checked we stopped hitting off a tee in a game at age 5.
Once again, this goes to the argument that metrics aren't everything.