For me, there is still a lot of guessing involved here. But you guys really might have a point. It would be interesting (at least for me) to compare two nearly equal games, like I said above. I will play some games against the same opponent next month, looking forward to check your theory.
And, I train my offensive side defenders and offensive/defensive midfielders (those that usually play at the 'borders'') with 35-40% - so I will see.
Btw, regarding training these non-position-A-skills, imho the problem is that we can't judge how good it is to train them. You can't see that in the ratings I think, just in team strength.
And for the umpteenth time I recommend to switch this discussion to the football formation thread - would be a good idea I think.