Sil's right.
It is a inconsistency. I don't know that I would call it Voorhees, but it is an inconsistency. However I will say it seems to be an inconsistency that is consistent with the Feral Predator over all. He's a bit of a messy brute.
But yeah, CH was absolutely retreating after getting shotgunned. He was using the respirator, which I don't care what anyone says, I still hold that has more to do with his injuries than it does the atmosphere. Jungle Hunter had no such issue and made that choice deliberately.