Fair enough,

Well, let me start by saying there are 3 waves of feminism. The first wave is vaguely classified as pre 1960s feminism, and is largely wrong. The ideas that were listed above all come from that era and even for that era are considered radical positions.

I thought the point of the gender/sex distinction was to separate the social-constructedness of being a woman or man from the biological facts.

This is the idea of 2nd-wave feminism. That gender is socially constructed, but sex is a biological fact. Presently this idea has been disproven. Among 3rd wave feminists (which is the most advanced form of the discipline) it is accepted that BOTH gender AND sex are socially constructed. How could that be you might be wondering? Well, biologically the human species is capable of producing 5 sexes: Male, Female, Hermaphrodite, Mermaphrodite, and Fermaphrodite. Hermaphrodites have both male and female genitalia that are capable of sexual reproduction. Fermaphrodites have functioning male genital, but the female genitalia are not capable of sexual reproduction. Mermaphrodite is the opposite. Each has of these sexes is anatomically different. You may be thinking "well how come I never hear about 5 sexes?" Well because for thousands of years in western, as well as many cultures, hermaphrodites, mermaphrodites, and fermaphrodites have been eugenically diminished. Up until the 1990s American and European doctors would tell parents their child was born with a deficiency and perform an "urgent surgery" to make them either more male or more female. These operations were potentially lethal; many places still perform such operations, only now instead saying they are mandatory, doctors socially pressure parents into opting for them. Using such methods as telling parents "think about the life your child would lead," don't you want them to be normal?" There is nothing biologically threatening about being born a hermaphrodites, merm, or ferm. The only dangerous thing about it is the social stigmas it burdens a person with. Anyway, the point is that a perception of what is normal (the male-female dichotomy) has resulted in the intentional out breeding of more sexes, thus making sex a social construction. If you would like to read more about this, or third wave feminism in general, I would suggest starting with Judith Butler. She is pretty much the matriarch of modern feminist thought. Her writing is highly influenced by Derrida. It has a post-modern air to it that at times is pretentious, but beneath that her ideas are really brilliant.