I’m a bit confused as to why the above matters.
If their gender is female then that’s what it is.
And given that it’s unlikely to be because of fairy dust, then there’ll be a physical explanation.
So then maybe we get asked, is/was it due to nature or nurture, or both? And again I’m wondering, what does it matter, for the purposes of acknowledging what their gender is.
Am I just imagining it, or is it the case that in between the lines of some of the things being said here, is there an implied suggestion that gender isn’t really real?
For the most part, I don't think it matters.
There are a few subjects where segregation on the basis of sex are reasonable and appropriate in my opinion. And for the most part, I'm perfectly willing to allow transgender people to be exceptions to that segregation on a case-by-case basis.
To some people, however, it ends up being a key element of their argument. The observed (but minimal and dot definitive) differences in brains gets used as justification for transpeople to have a carte blanche to circumvent reasonable sex-segregated situations. They claim that because male and female brains are different, and because some portion of transgender brains appear to be closer to that of the sex they identify with, then they have a female brain and are therefore indistinguishable from a female and should have all direct access to everything female with no questions asked. Like sports and rape shelters and prisons and high-school locker rooms.
It's a similar red herring to the intersex arguments. That one bothers me more though, because it's wrong on multiple dimensions. We've had several years of being told that sex and gender are distinct and disparate elements of a person, and that the significant overlap between them in common usage and perception is really just a coincidence because so many people have genders that significantly overlap their sex. When challenged with the argument that humans are sexually dimorphic, the topic of intersex ends up in the mix. Even though intersex conditions are very rare, and the majority of intersex conditions are technical genetic variations that don't have any impact on gender at all. The vast majority of transgender people are not intersex. And the vast majority of transgender people are not intersex.
It's a bit of a logical jumble. Gender and sex are distinct and separate things, except when there's sex-based science research that can be used to support the objectives of the trans community by conflating the two. To be fair though, the smattering of anti-trans folks out there do the same thing in reverse = they contend that sex and gender are the same thing... except in those cases where they're not and the separation of them supports their argument.
Reality is that there really is a difference between males and females. Physically, behaviorally, and genetically.
Reality is that there might or might not be a difference in gender that is something other than conditioning and brain plasticity around gender roles... but there really isn't anything that conclusively demonstrates this to be the case.