Tiger woods. I can't think of any tennis player who has been in the top 100 for the past few decades who didn't commit to it totally as a young child. Start tennis at 10? Too old. Swimmers. Has anyone stumbled into sporting greatness from being outside the top 5%? Or 1% when they hit adulthood?

So what is being said? A huge amount of elite success is in the hardware, i.e. the body &/or brain. These go through rather large changes between ages 10 an 18. Puberty. This shakes up the ordering among those who showed enough promise to have already committed to becoming elite.

What am I missing here? Seems like this research is nothing more than "Kids change through puberty, the nature and sizes of the changes are a bit of a lottery for each kid." Much like the the genetic factors are also a lottery so you can't reliably predict who is going to be great from the results of their parents. (But if your parents are both 5ft, the NBA seems an unlikely destination for you).