If you use the 2 short cuts (slicing the door and police car terminal), killing the adds will allow you to not have to go past the bonus boss to get enough kills to activate him. The 2 short cuts saves more time than not killing the pigs.
I think your confused. The adds will die from Wookie's flamethrower and instantly from his "Unstable Fuel" channel. This topic wasn't about not killing the adds; it was about not going over and standing on the taxi, which drags the fight out.