There's really only one rational way to discuss this:

https://en.wikipedia.org/wiki/Sexual_differentiation_in_humans

One of the more interesting aspects of this:

Most mammals, including humans, have an XY sex-determination system: the Y chromosome carries factors responsible for triggering male development. In the absence of a Y chromosome, the fetus will undergo female development.

Female sexual development is kind of the fail-safe option; male development depends on the presence of the Y chromosome.

For example in Turner syndrome (45,X0) a fetus develops with only the X chromosome (and only 45 of the typical 46). This always presents as sexually female.

But then that's not always true because there's XX male syndrome, in which a 46,XX individual develops male sexual characteristics.

Genetics gets progressively weirder: https://en.wikipedia.org/wiki/Sex_chromosome_anomalies

Many cases of these anomalies do not present significant health concerns and therefore are rarely identified (for instance, triple X syndrome (47,XXX)), which means that it's likely that anomalies are more common than what is represented in the recorded data. We simply don't have complete karyotype records for everyone born on the planet.

Basically, biology laughs at attempts to define strict categories. All we can really do is define what is most typical, and what is atypical, and of the atypical cases it's the ones that present health concerns which receive the most study. There is a lot of gray area.

And all of that only covers human sexual differentiation. Other mammals are generally similar (using the XY system), but have not been studied to the same depth as human genetics (because healthcare). And of course there are other systems.

So the original point is valid - "biological female" is at best a vague category with fuzzy edges and weird overlaps, with "normal" defined by statistical representation more than specific characteristics. Reality is too complicated to fit in neat boxes.