@suggestionsplease1 I did it. I typed "sex binary" into Google scholar.
Since the idea that sex might not be binary is only supported by special pleading, that's what I found. Very near the top cane this gem.
Volpe et al 2023. My summary:
'Cardiovascular research based on the sex binary excludes transgender nonconforming nonbinary and intersex people. TGNCNBI people represent between 0.3 to 3% of people depending on age group. Therefore (sic) research on cardiovascular health needs to be more inclusive.'
I mean - that's a load of old crap. Sorry but it really is. Of course cardiovascular research doesn't exclude anyone by being based on male and female categories, because that includes everyone, even if a tiny number of individuals have a more complex form of their sex.
It also strongly suggests that in cardiovascular research at least, pretty much all scientists do think that sex is binary and set up their research that way. Given the poor history of research into heart health of women, it suggests that we could do with a lot more binary understanding, and a lot less trying to mush women's needs into hiding under a big shiny gender lid.