Casual sex is not very stigmatized in CZ. You wouldn't be able to pull something like PH in PL for instance.
The sweet spot is around 2007 or so when 1) the producers felt confident enough to host parties with girls from outside the industry they invited for the background through ads and a "bring a friend next time" policy, 2) the producer's filming quality became good enough, and 3) the girls were less worried about the internet that never forgets.
Pretty much since PHGC the girls have been looking more and more like escorts rather than average party goers. Probably because most of them are. I guess the complaints from the real amateurs were growing and they found less random girls who would participate.
Here is an article from 2006 that gives a one sided view of how the parties were organized:
https://www.idnes.cz/zpravy/cerna-k...ky-hrat-v-pornofilmu.A060602_132319_krimi_ton
The complaints are probably one of the reasons why the editing seems so horrible. They cut away probably when a girl revoked her consent for the footage or there was some kind of dispute over it. This means, we might sadly never see the interesting bits that got edited out, even if they re-release parties as multi cams.