Could it be that you feel ‘not male’ so by default you must be female?
This is what I always wonder. It is such a BINARY way of thinking, and odd in a group of people who talk about 'fluidity' and 'spectrums.' [ach, 'spectra'?]
And it's also about gender, not sex - somehow, a man at odds with his male body (a really Cartesian mind/body split) sees stereotypes of femininity as 'female'? And then claims he is female, rather than feminine. It's rather confused thinking.
Then add to this the specifics of @Positrans ' tendency to call herself a 'girl' (from what they say about themselves, Positrans must be in their 50s or so?). I'm older than that, but we 1970s feminists stopped calling adult women "girls" a long time ago. IT's demeaning.
But it suggests something interesting about transpeople's possible fetishisation or fantasising about 'girlhood.' Little do they know or understand about what it is really like to be raised a girls.
That is, if you're one of the lucky girls in the developed world; if you're of the female sex in the global South, you may not ever reach being born, or live beyond childhood.