MidnightVT
Speaking from an entirely personal point of view, I have yet to find an AV game that wasn't HTML and using real porn clips, where the moaning and grunting were either done well/believable/didn't feel out of place or weird... more often than not they take me entirely out of the fiction/immersion, such as it is. But that's just me and your mileage obviously varies.
speaking not from a personal point of view: Z is very good with playing with his soundtrack and puts a lot of effort in ambient music, even for the sex scenes.
I think that the kind of sounds you are expecting are probably a bit disruptive to those music accompaniments, which doesn't make it necessarily undoable, but adds another layer of complexity that is of interest to only a fraction of the potential market.
That said, I can't exclude that some day in the future these extra sound effects might be added...but I expect it to be very much a "when the game is mostly done/the budget is high enough to do it really well and possibly do a whole voice over for the characters" type of deal. He does actually add the very rare and occasional sound bite, like the droplets of blood in a certain Fairy scene, or the sound of a gate or door being slammed open, more often than not in animations/cutscenes, for cinematic effect... but that's about it.
As of today, adding sexy noises during sexy scenes does not appear on the development planning log.