What they are trying to do with these new matchups, is to MINIMIZE the negative effect you have when playing players out of position, and NOT to let us train them in their correct places.
When you train Rebounds, if you want your SF to train that skill, you will have to play him as a PF or C (out of his natural position), and to minimize that they have this new matchups, so that he can play in offense out of his position, but still defend as a SF.
That's not what i would want, if i really wanna train ALL my players, and build a balanced team.
What we see now, with more recent teams (less than 10 seasons), is that they are very good in inside game (PF/C) or very good in outside game (PG/SG), because it takes 4 to 5 seasons to build a fairly good player in any of those positions.
So in order to have a competitive team, with fairly balanced players to play most tactics, you will need at least 10 seasons, but even then your SF will be less balanced than all the other ones, because that's the hardest spot to train, with no direct training (1 pos), and only minor secondary training (2 pos), and even then we can only train 3 skills (JS/Dri/Blo), without having to play him out of position, in order to get proper training.
What we need is to be able to train ANY player on his core skills (1 pos), and then some training on his other skills (2 pos), and some training on other skills (3 pos), and i give you an example below:
PG --> Pas+Han+OD (1 pos) / JS+Dri+JR (2 pos) / Reb+Blo (3 Pos) / IS+ID+Sta+FT (Team)
Now you can train most of these core skills, either on 1 or 2 positions training, but we would need a similar layout for SF:
SF --> JS+ID+OD (1 pos) / Reb+Han+Dri (2 pos) / IS+JR+Pas (3 pos) / Blo+Sta+FT (Team)
These are only examples, and that would expand to ALL positions, giving us a more balanced choice to train our players in their NATURAL positions, and if we choose so, in order to improve them faster and at our own expense (read throwing out games, leaving CUP competition earlier), we could STILL play them out of position, if we wanted them to train FASTER on any specific skill.