I agree with @Silas as this seems to be one of the most misunderstood things about Amorim's system. People always going on about the wingbacks like they are traditional wingbacks, but historically this was never the case in Amorim's system. And in fact it was one of the biggest problems for United this last season. What Amorim seems to look for are players who are strong off either foot, so they can go down the line or cut inside to create overloads in central areas - exploiting both overlap and underlap situations. He wants players who provide an attacking threat and creativity from those positions, but also have the legs to get back when needed and close down the spaces in defensive areas. He's been known to put defensive wingbacks in to close a game up, but primarily use converted wingers as his primary go to.
Much of this is supported by discussions he's had on the subject, that the primary front three of two 10s and a 9, needs to be supported at any given time by at least one of the wide players so the team is always attacking with four at a minimum. And this is with a proper attacking player in support, not a defensive player finding themselves in nosebleed territory.
At Sporting he used Catamo, Santos, Araujo and Quenda who are ALL converted wingers, why? Because they spend much of the game operating as wingers. Full backs are just generally the wrong profile for this system or it becomes too defensive.