> In other words, people who moved on from the gender assigned to them at birth.
Yes, and the Latin word trānseō (nominal form trānsitiō → English: transition) means exactly to "go on across", "go beyond". Trāns ("across, beyond") + eō, it ("I go, he/she/it goes") + tiō (→ English: "-tion"). It's a distinction without a difference.
My point is that they share a source and are siblings, but one is not the parent of the other. Being transgender is not about the medical or social transition, it is about how the person identifies.
What does it mean to "identify" with a claim about what society is like - namely that "binary" gender might be more of a spectrum, with weird liminal stages in-between? You've said that this is what "non-binary" is about. How does this even begin to square with all those other notions about gender identity being something exceedingly clearcut, that someone can base major life decisions on?
Yes, and the Latin word trānseō (nominal form trānsitiō → English: transition) means exactly to "go on across", "go beyond". Trāns ("across, beyond") + eō, it ("I go, he/she/it goes") + tiō (→ English: "-tion"). It's a distinction without a difference.