Maybe the coach is doing some experiment to understand why many good players and even goalkeepers play well in other teams but when they arrive at Manchester United they play worse, but strangely when they leave Manchester United they play well again.
Manchester United has made terrible mistakes in the last 5 years

Fiorentina will trigger the option to extend David de Gea’s contract, confirmed.
“He will stay with us also next season”, president Rocco Commisso says.
https://x.com/FabrizioRomano/status/1910935918502174981At this point he would be playing for Manchester United and the team would have saved money, but they let him go and spent money to sign a goalkeeper who didn't have much experience in the Premier League. Honestly, I can't understand Manchester United's mistakes.
It was clear from the start that De Gea would be good at any other club, as he is a goalkeeper with a lot of experience and proven skill. Onana had literally a couple of seasons at Inter at a high level. I can assume that it is easier to be a good goalkeeper at Inter than at United. Accordingly, the bet that Onana would be just as good in more difficult conditions turned out to be unfounded. This can be considered a serious mistake by those who wanted this transfer.