Quit it, swabs.
If i were Green, i wouldn't try what he did there, simply beacause i like my characters to epicly win completely on their own, or die horribly for failing to do so. But as i am just a bystander here, my only argument against that decision is that such a trick is indeed close to metagaming, introducing a third side to the battle, akin to when Khazna made his way out of Leeroy's explosion: something seemingly unacceptable during a fight, yet used twice already in the finale. The battle ensues between a fixed number of characters, and any NPC's are either summoned with an ability, or made zero-tier (unable to affect the battle's flow). But here, a character hastily brought into action actualy becomes a gamechanger, allowing for both murder and escaping. Maybe this isn't a rule yet, but it sure seem's like it should be.
Sure, this is getting old, but we can still prevent such things from happening in the future, rite?