One lot of scientists may well say that gender is not determined by chromosomes or genitals, but that may be because they are referring to the social construct rather than sex.
OTOH, or even alongside, scientists may well say that sex is not always determined by chromosomes or genitals, because they are referring to DSDs.
Neither of these statements is wrong in my scientific (I'm more qualified to analyse this than a lot of the 1600 "scientists") opinion, they are just being used by a misogynistic agenda to support ladybrain, when they do no such thing.
Finally, some scientists may actually believe in ladybrain. That proves nothing, there are scientists who don't believe in global warning.
People are human, and sometimes humans are stupid.