You know in hindsight it really would have made more sense of it was Amuro in the final fight.

Rather than trying to beat him (Because really who in that timeline/reality could've stood up to him in a fight at that point?) they would have to stall and try and convince him.

It didn't even have to be OG Amuro possibly a variant that noticed what Alternate Lalah was doing was causing more harm than good and came to end it the only way he knew how at this point.