I have zero doubt that's what happened. Sex=biology ; male=xy chromosomes, penis +testicles, etc / female=xx chromosomes, uterus+ovaries, etc , while "gender" is a grammar term , used for languages that have "masculine" and "feminine" words. It should never have been allowed to supplant sex.

HOWEVER, those previous generations were NOT 'the victorians', who quite happily talked about women "unsexing themselves" , who spoke of women "standing on the dignity of their SEX"...Victorians had no problem with the word sex, or recognizing the biological basis of the word, so one wonders just when people became so mealy-mouthed. I am guessing the 1940s or 1950s, but that's just a guess.