This is true for sure but I don't think, that this applies to what is happening on the pitch. No player is expected to play two positions, if a player drifts wide or tucks in, another player will take responsibility for the vacated space. If this is working is down to the quality of the plan and the awareness of the involved players. I know, you rate him higher than I do, fair enough - I also think, he will look a bit more natural in the middle of the park. But I wouldn't be shocked if more is needed than to just put him into another starting position. He looks overawed for now. Don't think, that this will fade away just because.
My feeling as well but we also have to note, that even better players needed time to adjust to the premier league and to a top club environment. I think, it is safe to say, that the physicality, skillset and probably mentality he brings, work in his favor, so there is hope. But I agree, I also don't see him as some sort of corner stone for the United midfield. But to be honest, not one of our current midfielders falls into this bracket...