See, that sounds as much like a “fad of our time” as anything, albeit in response to a different trend of our time
Sexual dimorphism is a biological adaptation for reproduction. Why are we so sure that it is an ontological or theological reality as well, such that to God even a person who doesn’t fit into the most common categories must “really” be one or the other? God isn’t biologically male or female, after all, though we usually speak of Him in the masculine.
Of course, if you’re right and there’s a sense in which even souls are inherently male or female even if their bodies are atypical and don’t show it, then the transgender folks have a pretty good theological argument. After all, they tend to be absolutely certain of their sex, even in defiance of the biological markers that typically go with it. If a soul has a sex, that sounds to me like the defect in a transgender person is in the body, as they say, rather than in the mind as some of us cis folks like to insist. If the fallen world can produce for someone a body of indeterminate sex (or missing limbs or whatever) without that being God’s fault, why can’t it saddle a male soul with a typically-female body or vice versa?
On the intersex issue, I don’t have an intersex condition per se, but an extensive digestive birth defect meant that both my internal and external sex organs were either absent or barely developed. My parents were advised that I was “most likely” a girl and treated me as such. I ended up entirely comfortable with that, so in the current terminology I’m a cis woman — but like a trans woman I took hormones from adolescence on and eventually had surgery to (re?)construct the appropriate parts. As far as I and everyone else is concerned, I’m a woman, married to a man and trying to be a good Catholic. However, since I have never bothered to check, there is a small but nonzero chance that I am chromosomally XY. Would you insist that I upend my entire life, leave my husband, and start living as a man at nearly 50 if that turned out to be the case? This is why I have a lot of sympathy for the trans people who are increasingly making themselves known; while I’m cis because my doctors and parents effectively guessed right, none of my lady parts are factory equipment and I’m quite happy being a woman even though it might happen that I have a Y chromosome tucked away somewhere.