I don't know, I'm no expert, just a nerd who reads too much and overthinks everything lol.
I suppose it would help if we can put forward theories about mental health manifestations from the past. For example, the hearing voices of the Virgin Mary thing: teen girls in the Middle Ages had incredibly dangerous and controlled lives. You had to get married to a man of your father's choice if you were rich; to whoever (literally) grabbed you first if you were poor. Then you were almost constantly pregnant and if poor, doing physical labour, so that your chances of living beyond the age of 40 was low if childbirth didn't get you first.
In this rather gloomy context, the Virgin Mary offers a 'way out': she had a baby but without sex, the baby just happened to be the messiah which offering Mary individualism, fame and freedom. More practically, hearing her voice could mark you out as special, which could offer you a practical escape from the nuptial drudge - you might end up in a convent, where you'd have a better and more luxurious life, or you might reach the heady heights of Joan of Arc - fame, freedom and fighting. Ofc you might also get burned as a witch but it might seem a gamble worth taking.
I don't think these women were pretending by the way I think they probably did believe the Virgin spoke to them. But it was a subconcious way of espcaping from the pressures of real life.
I think anorexia (as a former sufferer) can possibly be interpreted in a similar way, as a rebellion and escape from the HUGE pressures on women in the 70s, 80s and 90s: be thin but look healthy and fit too. Have a career but for god's sake make sure you don't become more successful than men. Have as much sex as you like but don't become a slut. In this context, focussing inwards and obsessively on making yourself smaller is quite a logical move for a mentally distressed person, tbh.
So we could frame gender dysphoria as some sort of subconscious cry of distress and rebellion against the demands placed on the male and female bodies today. What they are, I dunno. Instagram-enforced images of perfection? Porn? A focus on the body as an escape from an increasingly hostile work and economic environment.
Dunno. But it's definitely not that a make has a female brain or vice versa. It's a manifestation of mental illness and needs to be thoroughly researched as such so that a decent treatment pathway can be found.