It isn't Orion.

Instead, Optimus Prime stands on the other side of the containment field, his arms crossed over his chest. If his mannerisms don't go a long way to show Starscream how incorrect he is, his manner of speaking will.

"Starscream," he says, and that's it. No direct confirmation, no further taunting, just a dagger glare that Orion Pax could never quite pull off and just enough rope for Starscream to hang himself with.