I think you're on the right track, thinking of selection effects. I don't think the effect you mentioned explains why to expect something requiring very nearly 10k hours, even though there's some obvious truth to it. I take it you'd put a wide deviation around the (central?) 10k figure.

Careers and skills are rewarded precisely because they're useful. I think what you're saying is that prestigious careers are the ones that take many years to develop (5 years full time = 10k hours). I think that's mostly true if you amend it to include those careers that are more a combination of raw physical/mental gifts and training. It's also true that if something isn't sufficiently rewarding, few people will bother spending 10k hours on it.

Here's the selection effect I like: people who can never become masters (even if they try) drop out well before completing 10k hours of focused practice. If you look at the few failed masters who persist in spending 10k hours, it's easy to find things about their practice that you can call crazy: "can't you see that you're doing this part wrong? why aren't you working on correcting it, instead spending time on what's fun or satisfying or already routine?" In fact they may never be able to correct that thing they lack the gifts for.

I think that's nearly the entire story. Surely plenty of people with high talent nearly-peak (above 99% of their lifetime peak) sooner or (slow learners, or unusually deep potential) later than 10k hours.

I'd like to see what happens with people who are recreational athletes (basketball, volleyball, softball, etc.), not especially gifted in physical attributes, some of whom definitely log the 10k hours. Will it be accurate to say that those who actually drilled and rationally worked on specific skills based on analysis of their game performance, should be masters (limited from being pro-level only by their physical handicap)?