I think he still would have forcefully moved his thumb with his other hand to press it.I was talking about the ambulance running him over specifically.
Oh wait, here's another Araki inconsistency. Why does Kira have to physically press the trigger with his own hand yet Jotaro can ORAORAORAORAORAORAORAORAORA with his hands in his pockets? Or the fact nobody else with punch ghosts or sword ghosts or whatever ghosts doesn't need to mime the actions of their Stand.