When deciding what pronoun to use, biological sex clearly doesn't matter, when talking to a doctor, it may well matter. We can use the appropriate thing at the appropriate time, just as we do with, say, an adopted child, where most of the time you don't need to distinguish, but when it comes to inheritable disease it clearly matters. Likewise, saying "that female over there" when talking about a trans man is utterly useless to me because it doesn't help me identify them without pre-existing knowledge. Man/woman referring to gender identity clearly makes sense for casual conversation, someone's biological sex is none of your business in most cases.

Of course, our increased understanding also says that dimorphism is an oversimplification: the reality is that sexual traits are varied and it is much more of a spectrum, and better understanding of this medically should lead to more personalised medicine that is more effective.

This is especially true when it comes to trans people, if the issue is, for example, linked to oestrogen, then HRT can be more relevant than the chromosomes someone has.

I'm guessing (well, hoping) that everyone agrees that the male/female distinction is medically relevant. E.g., I'd get more from a visit to a urologist than to a gynecologist.

I think there's less agreement about the "di" part of "dimorphism". Obviously most humans fall pretty squarely into the "male" vs. "female" categories, but there's less agreement about there being precisely two, clearly delineated categories.

Some examples:

- hermaphrodites

- conjoined twins with different genders (insanely rare, IIUC)

- non-heterosexuals and transgender people, to the extent that those characteristics indicate underlying physiological differences