I don't think Garnacho wants to force a move out of Manchester United, Amorim doesn't want him in the team and so far no suitable club has officially come for him. So it seems like his giving the club an option, either they help him broker a deal between him and Chelsea or he remains at the club.
Alejandro Garnacho have benefits if a team have him in the frontline. Manchester United wouldn't know what they got until they lose it. In previous seasons, Manchester United have made quite good number of significant lose of players and that's totally not a good record for them. We can see clearly that every season, it's just another turn for Manchester United to lose players then the curious question rises again, what made Cristiano Ronaldo exits the door of Old Trafford? A legend doesn't deserve to leave the club as Ronaldo did. The same thing happen to Jadon Sancho, Marcus Rashford and now Alejandro Garnacho, common enough is enough.
I would perceive something sketchy in the team which is left untold. Secondly the fan base of Manchester United is so toxic, they only praise and give accolades to prime players and when this players in question experience fatigue and flop, the lashed at the first sight they see flopping performance, they give absolutely no room for redemption or a second chance. All these features is more reason I would support Garnacho to force his way out of Old Trafford and write a new chapter in Stamford Bridge.