No, troons didn't come up with those terms. Intersex people did. It dates from a more crude time in medicine where doctors would (with good intentions) attempt to surgically "correct" ambiguous looking genitalia. Problem is, a lot of times these genitals had nothing functionally wrong with them and they just looked funky. So you had doctors hacking, say, enlarged clitorises down to a more typical size, and in the process, maiming the kid sexually for life.
They sorta imagined themselves to be surgically assigning a sex from an ambiguous starting point. Of course, factually, the kid always had a sex, they just had what we now call a DSD, or a disorder/difference of sexual development. A girl with a large, sorta micropenis-like clitoris is still a girl. But medicine was more primitive back then.
DSD is preferred nowadays over intersex, because no one is literally between the sexes. The older generation of DSD people might still use intersex, but anyone young nowadays using the term intersex is probably lying about having a DSD to pretend to be a special snowflake to the rainbow faggots. I've encountered dipshits who don't even claim a specific disorder (Kleinfelter syndrome, 5ARD, CAH, etc), they just think "intersex" itself is the disorder. Like they'll say "oh I have intersex".