One, that makes no sense. Sex is a classification because it is part of material, empirical reality.

Two, intersex is NOT an example of more than two sexes. I am literally studying biology in university. That's like saying that because some people have a birth defect that gives them six fingers on each hand, that humans as a species don't have five fingers on each hand.

people need to read some biology textbooks. two sexes. behaviors are influenced by sexual dimorphism and natural selection over time. "gender" is a weird semantic construct that is rooted in dimorphic sex characteristics. Saying that "it makes no sense to talk about biological sex existing outside of its social meaning" is scientific denialism and total bullshit. We are mammals. Every mammal has two sexes with different behaviors in each sex that evolved over time for the purpose of efficient reproduction. This is partly where gender stereotypes emerge, some of them are rooted somewhat in reality. E.g., females are more associated with caregiving because evolutionarily, it is costlier to produce eggs and females must be invested in raising their offspring for it to be worthwhile. I say this as a woman. It's the reality of how our species has evolved. Doesn't mean that women have to fullfill this role, just it makes sense that it's associated with us. it's not that deep lol