I understand your point here, and agree with it, but I caution you strongly against using the term "gender" instead of "sex."
The human species exhibits sexual differentiation: a sexually functional male and female are essential to reproduction. Thee are two sexes, neither more nor less, and those sexes are readily identifiable by objective anatomical, physiological and genetic markers.
"Gender," on the other hand, is fluid and multiform: it's a social construct. Originally it was just a category of grammar (the masculine, feminine, and neuter forms of nouns and their modifiers in some languages) but now the gender activists have it meaning anything: hairstyle, employment category, affective response, dress, presentation, social role, preference, mood, style.
Don't say "gender" instead of "sex." In the present hostile rhetorical environment, to focus on "gender" is to concede all important points to the genderqueers from the outset.
>> [...] Thee are two sexes, neither more nor less, and those sexes are readily identifiable by objective anatomical, physiological and genetic markers. “Gender,” on the other hand, is fluid and multiform: it’s a social construct. [...] Don’t say “gender” instead of “sex.” In the present hostile rhetorical environment, to focus on “gender” is to concede all important points to the genderqueers from the outset.
I would’ve said there are just two genders for the exact same reason you say there are just two sexes.
To abandon the word “gender” because of “genderqueers” is to concede that “gender” is “fluid” and “a social construct”. Gender isn’t fluid ... it isn’t a social construct. It means the same thing a “sex” — and to differentiate the two is to fall into the very trap you’re trying to avoid.
SnakeDoc