It just not true. Andre posted a perfect example of a player with 13k who had only JS,JR and OD.
Maybe my English is not to good and i translate what i think using expressions from Spanish in a very literal way.
Im sorry if it sounds bad.
The play that Andre posted has sensational JS (2 positions train), prominent JR and strong OD.
We have to se the salary of a player that has sensational (12) RBD (2 positions trains), prominent (10) IS and strong (8) ID. And then compare the salaries.
I have seen this one (its hard to find but you can try):
(2671723)15k and 11 in Rebounding, 9 in IS and 9 in ID. It seems nearly the same, and the salary is nearly the same. (a guy with 10-10-10 in the primaries has a bigger wage than a guy with (13-10-7) in his primaries.
And like Ebustelo said, the game is the same for everybody!!! and if you see what happens when you train the 3 primaries (look at italian Shooting guards in the next wage update)... take a decission, but dont complain to change the game.