The entirety of sciences is based on generalizations of stuff by their common denominating parameters, despite the outliers. This includes chemistry, physics,...

Generally in biology, the female are usually characterized as the sex producing immobile ova and the males producing mobile sperm. The outliers, which due to some mutation or other reason doesnt fit that description, doesnt change the definition, they are simply described as outliers.

Its now also indicated by studies, that those intersex outliers in humans are mostly caused by endocrine disruptors during pregnancy but also during later life: https://journals.sagepub.com/doi/full/10.4137/EHI.S39825