My guess is that it can probably be either, depending on your setting. If I'm not mistaken, Gladiator is both 6.1 and 5.1. Get that, then you could compare.
What receiver do you have? On my RXV-1000 their is a phantom ex mode that matrixes the rear center channel from the two other rears. You have to turn it on though. On my material encoded for ex or es surround you can set up the receiver to detect it automatically. If you want to have a discrete rear center channel you can hook up a pro logic receiver to power the rear center.