I guess everyone has their own definition, but for me power fantasy just means having agency to the point where you can control most outcomes. Not so much "you are better than everyone else" but more like controlling the actions of the player character more precisely and as a consequence, not being put into powerless situations.
In a game where you get raped when you lose, that means having the power to win and overcome losing. Where there exists a possibility of getting ntr (for it to be ntr, I assume 3rd character/group is into your partner but not you, and only wants to have sex with your partner) breaking of the characters having sex (ideally before the whole interaction) and take your partner in front of them. Or simply the option to not engage with content that you don't like or having the ability to refuse sex. It makes the game much more interesting in my opinion, rather than having a linear story with no input.
As long as you have the option to change outcomes, i'd consider that power fantasy in this context, or at least that is the context Savin repudiates players having. Actual power fantasy trope is just being unreasonably powerful (and if the hero is unreasonably powerful to the point enemies aren't even an issue, then there is no game).