There needs to be a Futa, that has reach 100 heat. They'll go screw someone during the day transition, like how they 'attack' you when they reach 100 heat. As all what that permit really does, is allow Futas to screw other characters that aren't you.
Doesn't work for facesitting positions? I know there's currently no purely lesbian poses, but a few are available if you genderswap Null and still have sex with the NPCs.