These things aren't necessarily exclusive, they can depend on a team's philosophy - I haven't watched Scotland play (why would I do that to myself) but for Ten Hag's playing style, building from the back is an imperative and one of the cornerstones of his teams. It made complete sense to play Casemiro there rather than McTominay (who additionally was atrocious on the night, by the way).
There was an instance in the second half where we had a nice build up from the back, 2 or 3 players playing one touch passes to each, with one finding McT in midfield - there was a clear avenue for a one touch pass forward (maybe to Martial? Not sure), but rather than playing that obvious pass, he took time to control, couldn't get the ball out of his feet, and lost it to Burnley's pressure, which led to a chance for them. This type of instance happens all the time with him, he has neither the technique nor the vision to play in midfield, or anywhere in reality. This comes from someone who admires his attitude, but he just does not have what it takes to succeed at Utd, and I honestly struggle to think of a Premier League club where he'd be a starter.