Pogba is easily the midfielder who get's the most freedom on our team, and to be honest even as a "CAM" he'd be asked to defend as he does right now, every player here is asked for defensive contribution.
I don't believe football is as rigid as those numbers suggest, if we play 3-5-2, 4-3-1-2, 3-4-1-2... I don't think it matters really, formations are not symmetric, not every player fills their spot exactly the same as the one next to him, or the one on the other side of the pitch.
Some people turn crazy at the slightest suggestion of Dybala playing on a 4-3-3, or something other than not an specifically named SS. Messi plays on a "4-3-3" that has Suárez as a CF, yet he seems to be doing OK, even when he has been playing as a CF for the most part of the latest years. I don't think it matters where you "place" a player on a formation, they have their own style, their movements and tasks asked by their coach, formations are nothing more than a way to simplify it for people to understand them.