Star Wars: Question about Palpatine

I'm not sure if the films say definitively but when Palpatine's face becomes disfigured in Ep. 3 .... is it really due to Mace or does he just finally stop disguising himself as Palpatine's normal face? Because in the holograms of Sidious it's hard to tell but it doesn't look like Palpatine's face if I remember right, does it?

So is he using the force to change his face or am I remembering incorrectly? Because I think it's obvious he could take Mace at any time but is waiting for Anakin to help him, so I wouldn't think he'd let the lightning damage him like that.

I think it was just supposed to be because of the Force lightning bouncing off the saber. Its just that this fact is so mind-numbingly uninspired that it just became fan head-canon in some circles that it was a disguise all along. That would have been so much more satisfying. Though in the holograms in Episodes I and II, his face is normal underneath the hood. You can see his nose mouth and chin and nothing's disfigured yet. But the idea still could have worked from a POV that he was just masking his true appearance on a constant basis, even when alone.