That just isn't how it works if you're trying to describe things scientifically--you describe what's actually going on in enough detail so it's clear. For instance, if you have dsx mutant flies that can only express the male isoform in a genetically XX fly, you can say that, or you can call it a "masculinized female" but you're certainly not going to call it male or female without qualification, and while you'll talk about the "sex determination pathway" a lot, the term will be used very cautiously if at all when referring to the masculinized female flies because most uncautious uses will be misleading.

Furthermore, unless the survey is part of scientific research, we're using the colloquial definition, not the scientific one.

We do the same thing with gravity--a funeral is a matter of considerably gravity, but not because it attracts people with a force proportional to the inverse square of the distance.

You can't just skip to the end where everyone already agrees with how you want to use "sex". Gotta argue for it--which you have to an extent. But until everyone accepts the argument, there's still potentially pressure to clarify what one means.