My feeling is that Calliope talks about gendered classes as a thing bc for them, at the time, they existed in a very sharp gender binary, and saw the world in that way. I think though, that she's just... wrong. There's really nothing else that suggests classes as gendered, we only get it from them, and they're an unrealiable narrator. Like. Callie also thinks that the kids will get wings when they godtier.