They're probably talking about tomboy women, women who don't get dolled up into femininity but this is a massive cope on their part. I work in a gym and we get a lot of more tomboy type of women who come in with very short hairstyles and wearing nothing but t-shirts with sweats or basketball shorts and it's still very clear to me that they are women. I don't know how to explain it but when I see them in person and hear them talk and look at their face, it reads "feminine" to me. Meanwhile we have 2 trans-identified men who come in and both of them don't "pass" in my eyes. Admittedly two of my coworkers were fooled though. Anyway the two trans-identified men, one of them does "pass" when far away but up close you see how obviously male their face looks even with the makeup and especially the voice. The other one doesn't "pass" in either capacity.

Anyway, it's just a cope.