--Even if "only" 10% of elite kids go on to become elite adults, 10% is orders of magnitude larger than the base percentage of adults who are elite athletes, musicians, etc. This doesn't sound "uncorrelated" to me so much as "not as strongly correlated as one might expect."

The way that I read the original study was that only 10% of elite adults were also elite youth.

Not that 10% of elite youth become elite adults.

That distinction is the key and surprising. Elite level talent and training and dollar spending in the youth is not then well correlated with elite level practice in adults across many disciplines.

As in your country's elite youth training centers (science, music, futbol, Olympic sports, etc) are mostly wasting money.