It maybe didn't appear that high, but Rashford and Ten Hag both commented on it after the game, and it was something they were focusing on throughout the game. The number of balls United sent over the top, luckily most were offside, but you only get away with that for so many.
Emery should have asked Olsen to come out more as sweeper, or else dropped the line deeper.
But other than that, I think Emery had the team setup as best he could.