Sorry, I should clarify my question: does Valve actually face a significantly increased risk of chargebacks if it should be more liberal in its adult game rules.
I suppose that if consumer behavior is to have their adult game purchases and conventional game purchases on separate accounts, and the Steam platform allows for that, then that may be so.
These days Steam allows hiding games from your public profile by marking them as "private", meaning that people can't see that you own the game and can't see that you are playing the game (which is presumably what you would want if you were a fan of "Sex Adventures - Incest Family - Episode 9"). I imagine this is good enough for people so that they won't bother having a separate Steam account just for porn games, as having a single account is more convenient. There's a reason why people hate having multiple game launchers on PC.
https://help.steampowered.com/en/faqs/view/1150-C06F-4D62-49...