Since she didn't provide links to "those studies", I fail to see how you can assert that they're "plagued by small sample sizes and methodological flaws".

Intersex individuals (those who display one or more characteristics of both sexes) exist, and those characteristics exist on a continuum (M-IS-F).

As such, it's obvious that if the body can present the external physical characteristics (breasts, genitalia, etc.) of both sexes, then it can also generate internal characteristics.

This means that the development of features like reproductive organs, hormone levels, and secondary sex traits can also vary in ways that don't strictly align with a binary understanding of male and female.

For example, some intersex people may have chromosomes that don’t correspond directly to their external anatomy, or they may have reproductive organs that combine aspects typically classified as male or female. These variations can be subtle or significant, and they illustrate that biological sex itself, including physical characteristics and identity, is not a simple binary, but rather a complex spectrum influenced by genetics, hormones, and physical development.

In other words, it's a stretch to blindly assert science doesn't back this up just because the exact mechanisms are still "blurry".