I think the whole 'learning a new position' thing is a bit of a weak excuse. It's not like we put him at LB, where he would need to learn the fundamentals of the position. Instead, we put him on one wing instead of the other.
And the weaknesses he's shown are not really positional. It's technical. His dribbling is sub par, which means his main way of beating a man is by knocking it past him and utilising his pace, but that's not so helpful once you're in the opponent's third of the pitch because the space to run into isn't there. In those positions you need more technique to beat a player or create something, and that's not something he's shown to have in his arsenal.