I think my favourite part is how she frames the existence of two biological sexes like it's some ye olde crazy belief from the deep past, before science and Enlightenment. Yes, biological sex is just like witches, and miasmas, and a flat earth!
Back then, back in the mists of time, way back in er, 1970... " we thought gender really was kind of binary and defined by genitals; science has gotten smarter in the decades since and we now know it’s a complex interplay of chromosomes, hormones, primary and secondary sexual characteristics and other stuff, some of which is in the brain, not the pants, and also that quite a significant number of people are born intersex, and some are misgendered at birth, and male and female never were airtight categories anyway."
Aaaaah! She just conflates sex and gender all over the place! No, in the 1970s they thought that SEX was binary. They were correct about that, because it's a fact. (There are just two kinds of gametes, and just two kinds of sex chromosomes.) Sex is not 'defined' by genitals (you can still be male with no penis.) Rather, genitals are an incredibly reliable way of telling what sex someone is.
Scientists knew about sex chromosomes in the 1970s. In fact, they knew about the X and Y chromosome, and their role in sexual differentiation, since 1905. Does she honestly think that in the 1970s we didn't know about hormones and chromosomes?
"Some of which are in the brain, not in the pants." Is she arguing for sexed brains? So she thinks there's lady brains and man brains? The sexist trope that has been used to oppress women since the 17th century? And if she's talking about gender, it's not much better. Gender is a social construct. It's not innate. It's certainly not 'in the brain'. Babies aren't born desiring glitter and pink.
It's like she's just taken all the weird gender memes from Twitter and just spewed them out. I'm surprised clown fish didn't get a mention.