It's a much longer history & theoretical argument than I can go into here, but in 2nd wave feminisms, [I stress the plural] there WAS a move away from - or perhaps CAUTION - about insisting on sexual difference, in terms of biological essentialism.
This was because women's biology - sexual difference - has been used against us for thousands and thousands of years. Particularly menstruation (a source of fear amongst many men, and patriarchy) and childbirth. I am old enough to remember "Oh women can't do X, because they'll only go & get pregnant" & so on & on & on. In the 19th century, education was thought to be harmful to girls & young women, because we menstruate.
So it is totally logical that in campaigning & pushing for ALL the things we take for granted now - basically, equal treatment in all sorts of public institutions - some areas of feminisms of the 1960s and 70s elided or deliberately overlooked sexual difference.
That doesn't mean we didn't recognise it! We knew only too well who was being raped, who was being denied jobs because "there are no suitable toilets" , who got sacked when they got pregnant. And so on.