I think people misunderstand what they’re talking about: they think “sex” is how you look rather than “how your body is set up”. We often talk about sexing animals, and we quickly decide what sex someone is based on their looks. So when there’s a continuum of how we present, people think that means the same for sex.
It’s an understandable misunderstanding, but people writing scientific articles shouldn’t exploit it.
Thanks for the question - it’s a good point to highlight.