I agree in real life, the sex part won't be working, I think they're fantasists.
In the small amount of incel stuff I've read they absolutely think women are privileged. And that the good looking men get all the women.
They believe women can have sex whenever they want, but they gate keep it from men like them. And because all they want is sex, they think this is a massive privilege for women.
If they were a woman, of course, they'd be on their back 24/7, happy days.
The disconnect comes in that they're heterosexual men. So what are they crowing about? They cannot be crowing about having gay sex. Because firstly they're not gay, and secondly, they could be having gay sex as men, no need to transition.
That's why I think it's all online. Gay men flirting with them online, and women telling them their legs look amazing in that dress, you go girl.