Although Sancho returned to Manchester United, but there is no guarantee that Sancho will have the same good performance as Sancho playing in Dortmund. Because after all, previously Sancho also played well in Dortmund and then Manchester United bought Sancho but what happened was, Sancho's performance was not as expected so Manchester United loaned Sancho to Dortmund again.
We can't expect his performance in Man United will be as well as in Dortmund because the tactics may be different and Sancho may not play as the main player in Man United. We know there are 3 left wingers in Man United. They are Rashford, Garnacho, and Sancho. Recently, Garnacho is the most rising player on left winger position. I'm sure Ten Hag will choose Garnacho as the main left winger for the next season. So, I really expect that Sancho will leave permanently from Man United. Joining Dortmund again is surely a good idea.