if you were 12-13 and a potential olympian next year, they'd have you on the anorexia shit to keep you tiny so you can do the extra shit, and it can fuck you up for life.

if you were 12-13 and the age minimum is 16, they work on developing you more, because you still have 3-4 years before you're eligible.

If the minimum was 14, they'd have to kick the training into highest gear when the girls are only 12-13 as opposed to 14-15, which is a big development gap.