Faceoffs doesnt determine if a player is a C or W. For a couple of years jt miller played exclusively on the wing of pettersson while taking most if not all of the faceoffs. Sometimes anders lee takes faceoffs for barzal even though he hasnt played C since college.
Center and wing is determined by positioning and responsibilities during play, not faceoffs.
As for stamkos hes a W now though he did fill in at 1C while point was injured. But when everyone was healthy he played W.