I don't know the exact answer, however you have to keep in mind most pros learn as kids or early teens. Kids learn at a much different rate than adults, and they pick up skills far easier than adults do. The key development years for a kid trying to develop into a professional sportsman is roughly 11-16 for boys and 10-15 for girls.
The ages and ranges may be a little off but you get the idea. But this explains why someone like Wu could start at 10 and win the world championships at 16. Adults need a bit more time to develop their skills and I think probably practice more deliberately since they they aren't building motor memory as quickly.
For more info, check this out. It's not about pool but about talent identification in general for developing kids into professional sportsman. He also debunks the 10,000 hour 'rule'.
https://www.youtube.com/watch?v=1SZBBXddQxI
I think a huge part of the difference between how kids learn and how adults learn is fear and expectation. Kids aren't afraid of trying things. They aren't afraid of looking foolish for the most part and they don't hurry the process because they hone in on what they like about something and do that until they master it.
Adults like to set expectations and goals and plan to meet them. They set up practice routines and track their statistics. And generally don't take the time to hit a shot 75 different ways just to see what would happen. The don't play 25 shots off the corner of the side pocket trying to see if they can make the cueball does something cool.
I think the hand/eye coordination is important at a young age and it's possible you can't develop it later or build new synapses or whatever the prevailing theory is today. But I've seen people pick up all kinds of pursuits later in life (including pool) and almost instantly get to a very high level. But not without a lot of time and a lot of joy in the process. And a little bit of a plan.