They keep men around for brute labor and implied sex, all the men are collared and submissive. It was a point of friction between them and the hunters, who would generally rather men didn’t exist at all.
Ah yes, I remember now. Didn't one of them tell Percy he'd "look good in a collar" or something? In hindsight that was a weird segment for a kids book, maybe Rick has a bdsm thing he'd like to share with us. The Femcels of Artemis were a lot more fun (and memorable).
Weirdly enough, I think he could have actually used the Amazon uno reverso aesthetic pretty well without changing much at all, especially if he wanted to use it as a reflection of traditional gender power imbalance for his teen audience. A man saying he wants to force his wife into submission should be just as gross as the Amazon Queen saying she wants to buck break Percy.
I think that he was more interested in depicting 'slay kween girl power' vibes rather than a discomforting reflection of the misogynistic depictions of male-female relationships in media that could be easily absorbed and digested by his teenage male audience.
And don't even get me started on how Riordan ruined Nico. He was loaded with motivations and a really compelling story, imagine being from WWII era Italy, being locked in a hotel for 70 years, being the son of the god everyone hates, and losing your sister, who was your only family. His resentment and anger made him a wild card, and Riordan completely ruined him by making him a fag. It was all because he had a crush on Percy??? Really??? I remember being annoyed when I got to that part of the book and now it makes my blood boil, because Nico was one of the few good characters (new or old) that Riordan had in the HOO series, only for him to become defined by his relationship with Will Solace.
To be fair, what ruined him was the squandering of all these compelling character motivations which work independently, but he thought he was being clever because these can be read as painful gay origin story tropes. Parents regretting your existence, local culture hostile to gays, locked in the closet (hotel), abandoned by your family, etc.
It was a daring choice having him get manipulated by an older man who feeds on his youth, another very entrenched gay trope, though now far more taboo (cuz optics) trope.
He more or less accidentally built up a great potential character by pooling tropes, and then totally failed to recognise that it was growing to be more than the sum of its parts. Really could have taken a lesson from George R R Martin here, and gone the 'let your character grow' gardener author path.
However, think the reason for the gay revelation being more or less the end of his character arc is that at that time, coming out or realising your sexuality was seen in the mainstream culture as the climax of the gay experience, and that once you were past that, you just crystalize and live your life as a gay man like all the other identical gay men, and nobody wants to know about it. Everything after his coming out is surplus, it was all built towards that revelation, that climax of his arc. Now he's like Gohan in the Buu Saga, the character arc was completed in the Cell Saga, he has nowhere further to grow in the story, and he's basically happy with his lot in life.