[Den-O]

But it isn't a powered up form. His name literally means True, as in True Zangetsu. That's an entirely new suit, not an upgraded form of his previous one. He doesn't even use the same driver to access it.

If you want to argue that Kouta will steal his Melon ELS to use Jinba Melon and then he'll be forced to use original Zangetsu, then I can sort of see where you're going. But as is there's literally no reason for him to revert to a lesser power set. Look at G3 VS G3X for a good example of that.