Ahegao kinda works in this particular game. Probably just art direction itself helps a lot.
As I've seen actual release CG scenes and read the subtitles for these scenes - now it makes sure to show you she's not getting pleasure out of this. Well, only when she's on drugs/brainfucked or that event CG I noticed in the archive. So, mostly just a 'rape victim look with eternal suffering'.
So yeah, I find it curious that CG animations originally does include a complete corrupted mind broken female characters faces with tongues out which enjoy it in the end.
Seems like a shift in a middle of development. That also explain why it didn't really went anywhere with pregnancy mechanic and some other stuff like 3 character states were mostly scrapped/simplyfied (normal, weakened, nympho).