Yeah I found it true, when we invest SP to SA or extra positions our players still gain,
I have a 3* MR I bought him on level 2 at that his quality 29(5*) I gave him extra position at starting AMR+MC then I trained him last season(level 5) wow he gained 70+ in practice match, when he hit 34Q he have became slow then he played some matches he's now 36 Q, I'm adding him SA( 5sp left to complete his SA)