He does. I'm not sure its necessarily hiding, but he really has poor positional awareness on and off the ball. That means if we play out of the back, especially in a double pivot, Mctominay presents a gap in our build up, which affects us, especially in games where we are dealing with more pressure from the opposition. The fact with Mctominay is he really should be nowhere near the starting lineup for United and if I'm being honest, I don't think he's versatile enough for our bench either. Positioning and off the ball movement are the most important tools to a midfielder in the modern game and he just doesn't have it.
Nobody can know if he does it deliberately (presumably because he doesn't trust himself to take the ball on and play it forward) or if it's an accidental thing he doesn't realise he's doing, but the end result is the same. Scott constantly makes himself basically impossible to pass to because he moves behind opposition players. Many of us were talking about it long before that video was made. It is especially noticeable when we are trying to play out from the back, as he makes it far more difficult than it should be with his terrible positioning and movement. It's not like he just finds himself in these positions, he actively moves and jogs around staying behind opposition players the entire time.
It's something that he needs to improve, but he hasn't really shown any improvement in the years that he's been in the first team yet. In saying that, it sadly wouldn't surprise me much if the previous managers and coaching set-up never even really worked on it, whereas I have no doubt that ETH will be focusing on it.
You are both entitled to your point of view, but as of yet I haven't seen any evidence supporting this conclusion having watched him play similar midfield roles both for Manchester United and Scotland. I am open to reconsidering that point of view if you wish to point me in the direction of some convincing evidence - otherwise I am content to maintain my own judgement on this topic.