The youth academy page has been changed during the final update of the season.
From now on, when you promote a new young player, you won't have the same exact chances of having any traits. The chance of having a trait is a bit more linked to the player position.
So, as an example, if you promote a defender, some traits will be chosen more often than others.
The difference is small, but will lead to create more all round players.
Another season has passed, and traits on 21-22 years old will start having some impact, in particular in those players having multiple positive traits for the same position.
Good luck in finding them!