You're a funny man.
I may just be dumb here, but how many examples do you have for NBA players that learned skills from scratch during their NBA careers -- something that they never really did before, and didn't show any natural aptitude for. The closest I can think of is Kidd, but even he had 200+ college three pointers, shot 33% in his sophomore NBA year, and never looked back.
This isn't a skills from scratch though, but something he had yet to fully implement into his game as an NBA player until recently (you know in a season after a back operation and then suffering an hand injury during the season).
But what you seemed to be alluding to was the shot selection bit, and sorry to tell you, but practically none of the NBA players are particularly good at that aspect when they arrive, so the "since 16 years old bit" is a bit absurd.