You only think that way, because all of us here want anal sex. If you consider for a moment that the male character prefers pussy and / or dislikes anal, then anal sex that could be seen a form of sexual torture in a femdom game. "You don't deserve my pussy" sort of thing.
Or perhaps, I have experienced anal sex on regular basis in real life and have never ever found an actual woman (cis-gender female, if I must add) that would say anything such as "you don't deserve my pussy, boy, thus I'm going to dominate you with my sphincter. Assume the position, you pathetic buttfucking slave!"
If I'm being indiscreet, it has always been a mildly dominant act on my part, not theirs, in all the aspects: from controlling the pace and depth, the angle of attack, the duration, additional stimulation and that little mindfucking I would do, telling them their pussies now looked so beautiful, wet and abandonded, that I might never want to touch them again, just watch. And then I'd tell them to watch with me.
Receptive anal is arguably the most
submissive kind of penetrative sex one can imagine, and no amount of gender play or psychological role-reversal is going to change that. It's just simple physiology: very scant natural lubrication and the muscles structured in such a way as to expel rather than absorb - unlike vaginas which, all my anal obsession nonwithstanding, are admitedly the organs best suited to handle dick. All it takes to find that out is to try and stick a finger up one's own butt, just like that, no prepping. And then decide which one is the invading force: your digit or your assring.
I just can't picture a convincing dominatrix wearing a buttplug all day long, taking regular enemas and then lubing herself copiously, so she may teach a lesson to a male penis by, I don't know how we should call it, cruelly jerking it off with her well-trained unforgiving rectum?
Receiving tossed salad is an altogether different story, and traditionally it is perceived as an act of dominance, hence the expression 'ass-licker' to describe an overly obliging person. But someone who penetrates butts with either a penis or a dildo or hand would be commiting an act of submission this way... ? It's just as realistic as bunnies hunting wolves by entering the latter's stomachs. And then as the wolves shit out the undigested bunny parts a few days later is when the assrape happens.
Even fantasies should ultimately be firmly anchored in what we can all agree is real. So let's stop pretending that there is such a thing as a female dominatrix teaching boys lessons by 'raping' their dicks with her almighty peach and then complain there isn't enough fapping material dedicated to that. At some stage, seeking curiosities, or inventing curiositites just for the sake of it should stop.