Historically, globally, throughout history there has always been such outliers (Gender in Bugis-Makassar society, Sistagirls in Torres Strait groups, etc).
> when we've been running with a definition of
The "we" in a global setting and sans context is an issue, there's a plurality of definitions that are used depending on focus and degree of technical detail.
Richard Dawkins use of "sex" in recent interviews is a classic example, he deftly occludes the 2% of humans that don't neatly fall into M|F buckets by taking a strictly reproductive evolutionary razor to the question and responds (as best I recall) that "there are only two (reproductive) sexes, Males (viable sperm producers), and Females (viable egg producers) .. that's just (reproductive) biology".
That's a bit of a mean spirited one way mapping from two reproductive buckets to those humans that cleanly fall into those buckets.
Dawkins avoids and hopes the audience doesn't press on whether all humans fit into one or the other bucket (they don't) and of course his interviewer at the time doesn't press.
(The interviewer was Piers Morgan who famously can only handle bicameral two party systems: https://www.youtube.com/watch?v=JD7Ol0gz11k )
> a definition of sex that assumed a natural expression of hormones.
that assumed a majority case expression of hormones, sure.
Still, exceptions have always existed, been recognised (whether embraced or hated), and sometimes in history been given a place as part of society.
I think there's a significant point being glossed over here. You are suggesting that it is which hormones our bodies produce that determines sex, without regard to whether our bodies produce them with or without deliberate intervention. I don't particularly care if we settle on one or the other but it seems somewhat disingenuous to imply that this has never mattered when we've been running with a definition of sex that assumed a natural expression of hormones.