From what Sporting fans have said, he started off playing fullbacks in those positions (albeit being played very offensively). Then after a year or two he changed one of them to being a winger, and later changed the other to a winger as well.
So it could go either way. He may feel he needs fullbacks there at first to keep us somewhat solid while the team gets used to what needs to be done, and then eventually change one (or both) to a winger so as to overload the attack. Or it may have been a case that he was experimenting with the different tactics, and he's now set on having wingers there straight away. None of us will know until we see his first few games (indeed it wouldn't surprise me if he's not set on either yet and he'll be experimenting to see which works best with us).
Things changed and evolved from season to season but it also had to do with Sporting budget limitations. It's pretty hard and expensive finding a fullback that knows to attack/defend and has the stamina to do so.
Sporting academy has a long history of wingers so its easier to develop and teach a winger (Geny Catamo, Quenda...) on how to defend, since they already had the thing you cant exactly teach which is flair, dribbling, etc.