I already had this model on hand and converted to OBJ from when I was working on that skeleton mod (was looking into differences with modeling and UV mapping in all the head models, it's actually pretty inconsistent)... so here's PEPP_HRhead.msh:
There's not even the top of the head and stud under there, there's just the hair.
The hat is a separate model, NPCs can also have their hats/hair changed to it, as I'm sure you've noticed if you've ever played with that feature.
In IXS, the hair was made part of the hat model and the unseen bits were removed, and he has a normal minifig head, as you can see with the bug where his hat sometimes briefly disappears (or with modding). It seems Xiron got the hat/hair part of his SFM model from IXS.