I'd argue that he was neither a winger (in the mould of Giggs, etc), nor a striker (in the mould of Kane). If he had those stats as a genuine winger I'd be more inclined to agree.
The problem with the whole G+A stats is that they are clearly always going to look twice as good, as you are essentially crediting two players with one goal. If Rashford wins 10 penalties, all converted by Fernandes, and Fernandes plays 10 through balls, all scored by Rashford then using your metric Rashford has 20 G+A, AND Fernandes has 20 G+A. Which would imply 40 goals, whereas the reality is that it's still only 20 goals in total.
Scoring 70 goals in a season (7 players each scoring 10 goals) is not that impressive and won't win the league, but it sounds a lot better if there are 140 goals or assists (7 players each getting 20 G+A) in order to achieve those 70 goals.