He's not a winger becaue he's generating assists from the wing?
I'm confused.
Yes you are confused. Playing a center would increase his assist generating opportunities, which are obviously his strength. And would therefore increase overall scoring opportunities for the team.
Playing him on the wing decreases those opportunities because the boards are immediately the the left of him and he would naturally have less opportunities for an outlet for his passes. That's why the best play makers play center and not wing.
Bournival just scored another goal. With Gionta, MaxPac, Prust, Gallagher, Bournival, Bourque you have 6 decent goal scoring wingers to go with Eller, Galchenyuk and Plekanec.