Pedantically, all words are made up. I'd assume GP is using it because they see utility in a unambiguously-singular gender-nonspecific pronoun, opposed to the more widespread but somewhat ambiguous singular "they".
Yeah I also realized my wording probably wasn't right.
I meant to say words not known by most of the English speakers which can also not be found in the big dictionaries (to be fair Oxford had it, but Merriam webster didn't).
Especially when there is an established gender neutral pronoun: they
