There is a version of Mistress that uses it for all the sex scenes. There was such a backlash from Patreon, that Nini went back in and did "standard" sex scenes without the curtain. Let's face it ... people want to see explicit sex. I thought it was an interesting experiment, but the majority on Patreon wanted their "pound of
flesh", so to speak, so she changed it. Both versions exist.
Nini, also uses the "door ajar" peeping technique at times, like in Supporting Education, where husband and wife have sex, with the kid watching through the cracked open door; Penny complains when the husband can't "perform" .... part of the kid's nefarious plan. She even used beer bottles as a screen in Tribal.