You can still argue this as a GROUP rather than on an individual level. On average, historically and over time, women’s biology has been used against them and used as a reason to oppress them. The fact that the category of “woman” includes the infertile, some woman identifying intersex people, and trans women, doesn’t preclude the fact that for 99+ percent of women this holds true. And since the average or rather the bulk total is what informs society, this means that the proposition that “sexism is largely based in assumptions about women’s biology” can hold true when speaking about women AS A GROUP but may not be true when talking about individual women (or men).

For example, it is a truism to say that men are physically stronger, more violent than women ON AVERAGE. That doesn’t mean that small, weak men don’t exist. Or that violent women, bodybuilding women, don’t exist. But when talking about a category that encompasses 4 billion people, some averages have to be made. We cannot lose a useful heuristic that describes the large patterns in GROUPS simply because of the existence of outliers.