I guess gender dysphoria, if not a new phenomenon, is at least new enough as a researched field that there's still a lack of data and info available, but it's irresponsible of her to make some of those assumptions in the absence of more hard data
I wouldn't say it is not researched, it has been researched for decades. Medical interventions began in Western culture in the '30's. It's more the quality and the breadth of the research has improved.
The dysphoric aspects had to be approached more psychologically because the medical aspects either couldn't tied to one's internal experience, or you had certain theories fashionable at the time (like Ray Blanchard's autogenophylia) obsessing over male-to-female oriented individuals and viewed them as gay men who changed their bodies either because they were gay and wanted to justify their love for men or were obsessed with erotic self-love, the self as the opposite gender. it was all about sex, in other words, and there was a lack of exploration (not nearly as much) into the female-to-male experience. Overall, what existed tended to shoehorn gender dysphoria into some aspect of sexual orientation.
One big issue is that science itself (not just tied to this topic) was still developing. For example, there was no way until maybe the last 2-3 decades to study brains without dissecting them... which necessarily comes after death. Brain structure differences were noted, but in the case of trans-oriented people who might have had HRT, they couldn't determine whether the brain structure differences predated the HRT or HRT created the structural differences. There's been much more progress with the advances in science, the ability to identify dysphoric people earlier and willingness to enter treatment or study of some kind, etc. Lots more data too on post-transition contentment, which improved with better medical treatment. Also, despite all the furor nowadays politically, there's been a vast improvement socially in terms of not being ruined by transitioning. It used to be where you couldn't visibly fit in, and you'd lose your career / were living close to poverty level, you can now reasonably maintain family and social structures so that you are not alienated, etc. So obviously all that factors into post-transition outcomes and contentment. [Approaching this pragmatically -- if they cannot quantify one's state, one can at least look and see if and what treatments help long-term.]
So the quality and breadth of research has improved. But it still relies on an internal experience, versus something easily quantifiable (you can't get a blood test to determine your condition and how to resolve it), so... it still involves a psychological/therapeutic element.
