Whether you signed up for it is they key distinction. Suppose you had signed up for sex with your boss, but then he also also asks you to do the laundry - which

Whether you signed up for it is they key distinction. Suppose you had signed up for sex with your boss, but then he also also asks you to do the laundry - which wasn't part of the deal. That's bad. Vice versa may be worse, but either is bad. We wouldn't consider it fair just because it doesn't involve sex. In either situation, the power balance is the same. Your boss doesn't get more power just because he asks for sex instead of laundry.