Not many games have they played under him therefore it's not worth saying that Manchester United haven't gotten a lost under hime. He has played only 2 or three games. After playing as many as 5 game, he would have conceded defeat. But unfortunately he won't be handling the team after the next game. The main new coach will be taking over.
It's true. With only two matches so far, it's hard to say Manchester United are improving and Nistelrooy is a good coach. He shows some signal of being a good coach in future, but now he has many things to do, more time, more matches to prove his management capability. Manchester United will be coached by Ruben Amorim, not Nistelrooy in future so Ruud van Nistelrooy can enjoy his short time as a head coach for Manchester United. He might have another chance to be Manchester United head coach officially, not as a temporary replacement.
Although only two matches led by Ruud van Nistelrooy, but the results are not bad at all and also, in fact Manchester United played better under Ruud van Nistelrooy compared to when they played under Erik ten Hag who seemed to have great pressure. Also, there is still no guarantee for Ruben Amorim to be able to succeed at Manchester United, because basically Ruben Amorim also has no experience to be a player and coach outside the Portuguese league.
Thus, there is absolutely no guarantee for the good results for Ruben Amorim later and also, I think it would be better for Manchester United to entrust the coaching chair to Ruud van Nistelrooy first, at least until the middle of the season or until the end of this season. Because I think, Ruud van Nistelrooy has good qualities as the head coach of Manchester United.