Actually, it's the other way around. Gender and sex used to be
wholly unrelated concepts. In fact, gender used to refer to language/linguistics. (Hence, the amusing-but-outdated saying, "words have gender; people have sex".)
The idea that gender and sex are basically synonyms is nearly younger than I am (and at least one of my dictionaries still lists it as informal
). The idea that people
can have gender distinct
from their sex is slightly newer than that, but not by a lot, and it harks back to the original definition of gender. That said, all these definitions are
in the dictionary, so calling any
of them "wrong" is...silly.
"Existential Despair" is an oxymoron.