The idea is for Mount and Bruno to push high and one of the defenders to tuck in beside Casemiro to create a box midfield. The same set up Arsenal and Liverpool are using.
However, while Liverpool have their own problems (namely no DM), the player they will have tucking in beside that DM whenever they get him is TAA, who is obviously excellent in possession.
Meanwhile Arsenal don't just have Timber (excellent on the ball) and Zinchenko (regularly played as a midfielder) in their inverted role, but even used Partey (an actual midfielder) as their nominal RB in their last game.
In our case Bruno and Mount are doing what they're supposed to do and pushing high into attacking positions, but I don't see how they get sufficient quality of support behind them. Unless that gets addressed it will be very difficult for this to work. We need whoever is stepping in to take up those central positions to be very good on the ball, because they're basically playing as an auxillary midfielder.