I have 6 playstyles unlocked. The one that was already unlocked at the start is growing more quickly than the rest, he is 19. But I have a very good AMR with lowest % among the starting 11, but is the best scorer in the team and he is 26yo, he is gaining playstyle points more quickly than other younger players, 18,19, 21. ​

I feel more playstyle points are given to good performers and maybe to fast trainers? I don't think age is the most important factor here.