They're not edge or corner cases. What we consider male and female is socially constructed around presumed reproductive roles. This is the biological component. Every human society in existence would presume my sex is female because I am phenotypically female. Only a geneticist would add the caveat that I'm karyotypically male (if I even am - who the fuck knows cause even in the 21st century we don't do chromosome testing at birth). Let me also remind you that the gender/sex distinction is historically new! Most human societies would agree that I have changed my sex. It's only in the 20th and 21st century that people would dispute that, because the idea that sociological sex and biological sexes (whether it's genetic or reproductice or something else) are the same has become widely accepted. Speaking of birth sexing, sexes are socially assigned at birth according to genitals. This is why intersex babies get "corrected." Yet not all intersex conditions are obvious by looking at genitals. What would you call a condition that causes "females" to have "male" secondary sex characteristics? That's an intersex condition. Yet PCOS does this in up to a fifth of some female populations yet society does not consider it an intersex condition. Because patriarchal society insists upon the sorting of everyone into a sex binary (an immutable one at that, nowadays - a clear reaction against transhood) despite it clearly being bimodal and malleable. The body is artificially sexed. Women are not naturally hairless, yet body hair is considered male. The everyday Mesoamerican woman was as ripped as a professional kayaker from all the corn grinding she did, but the female sex is seen as dainty. The anti-trans movement wants to ban trans women from chess, darts, and Jeopardy! What is this if not 19th century sex science claiming women have inferior intelligence and motor skills?! Finally, let me remind you that humans are capable of generalized labor, and are thus able to change their environment. As a result, we have created exogenous hormones and sex reassignment surgeries. Trans people could change their sociological sex centuries ago. Now they can change their phenotypical sex. It is only a matter of time before we start growing reproductive organs from our own cells and having them surgically implanted. Nature is unjust, but we can change our nature!