The fascinating thing about this is that, in context… it’s still fucking weird, but for different reasons.
He’s technically joking about how it makes you transition, saying it’s a claim he heard from “scientists.” So he wants to call men women as a misogynistic insult, but also to poke fun at the concept of scientific study. It’s wrong to distinguish between gender and sex as part of evidence-based medicine and basic conscientiousness. It’s cool and good if you’re doing it to be a dick, though. He’s got to police gender roles, but also insist that they are completely immutable based on your sex.