I think a lot of this sort of thing was going around in post-Sexual Revolution social SF. They were doing the usual thing of extrapolating some then-current trend in a linear or exponential way, and the particular trend under examination (for reasons that are not hard to guess) was promiscuity rather than feminism. So everyone in the future is a swinger, but women are still chattels, they're just chattels that men tend to share or swap instead of hoarding them.