Inhave youth trainner lvl 4 and i was trainning 1vs1 and an 18 years old had a pop in blocks
Crosstraining means that 10% of your training is affected elsewhere. You can have strange pops sometimes if your player has a high skill (0.95) and it happens to be trained.
I agree with that, youth trainer helps to that 10% that the player train by his own, for me with level 4 on that i had an amazing results, 4 players with 19 years old pop at least in one skill extra, one of them got 2, JR and RB training 1vs1