This is overstated. They used genus contextually, in an abstract sense, for biological sex, in the same way we might use kind for a brand of soda ("what kind of

This is overstated. They used genus contextually, in an abstract sense, for biological sex, in the same way we might use kind for a brand of soda ("what kind of soda do you want?"), but genus didn't have the concrete meaning of biological sex for them any more than kind has the concrete meaning of soda brand for us. It's the same for Greek γένος, e.g. in Plato's Symposium: > πρῶτον μὲν γὰρ τρία ἦν τὰ γένη τὰ τῶν ἀνθρώπων, οὐχ ὥσπερ νῦν δύο, ἄρρεν καὶ θῆλυ --189d It's fair to translate that into modern English as "Originally there were three genders [or sexes] of human being, not two like now, male and female", but the specific meaning of sex or gender isn't there, just kind. It's a general word being used in a general way (literally, in fact: genus -> general).