It's not the same argument. He's asking to literally bend time to defy his age, something that has literally no scientific backing in any fields. There's actual medical research to prove and understand how being transgender works and why it's a real thing. These aren't the same thing.
One can draw a line in the sand between this and being trans without invalidating the trans community.
Nothing conclusive. If there is, post it. All I've seen are studies that, "suggest that," the brains of transgenders do things like the desired gender, or a genetic trait has been identified that, "could be," etc etc. And its clear that these studies were conducted with the specific purpose of finding such evidence - confirmation bias is an issue. You used the word, "prove,"... I don't think we're there, at all.
I got this from an earlier post of mine, too much trouble to re-type it:
The idea of "sex" and "gender" being different, distinguishable things never existed in Western culture until the 1970's, and then only among radical feminists. Before that a person might be a homosexual male, or a homosexual female, but a person's sex was based on biology and the use of the word gender was mostly confined to Spanish class when you were taught about how to use "las" and "los." Whether you believe in this transgender theory or not, if you discussed this with anyone before 1970 they would think you're fucking nuts. After 1970 until about 10-15 years ago, only 90%+ of the people you spoke to would think you're fucking nuts.
Please read about "Sexologist" John Money and how he invented the modern usage of the word "gender." Until mid-70's sociologists latched onto Money's theory, humans with a penis were males, and humans with vaginas were female, PERIOD. Next, read about how Dr. Money totally fucked up David Reimer in childhood with a sex reassignment attempt in infancy, took photos of Reimer and his twin brother in nude, simulated sex acts as small children, etc., and how Reimer eventually committed suicide because of his life being ruined by the man who came up with this mess of thought. This was the origin of transgender theory.
https://en.wikipedia.org/wiki/John_Money
Sexologist John Money introduced the terminological distinction between biological sex and gender as a role in 1955. Before his work, it was uncommon to use the word gender to refer to anything but grammatical categories. However, Money's meaning of the word did not become widespread until the 1970s, when feminist theory embraced the concept of a distinction between biological sex and the social construct of gender. Today the distinction is strictly followed in some contexts, especially the social sciences and documents written by the World Health Organization (WHO).
https://en.wikipedia.org/wiki/David_Reimer
Reimer said that Money forced the twins to rehearse sexual acts involving "thrusting movements", with David playing the bottom role. Reimer said that, as a child, he had to get "down on all fours" with his brother, Brian Reimer, "up behind his butt" with "his crotch against" his "buttocks". Reimer said that Money forced David, in another sexual position, to have his "legs spread" with Brian on top. Reimer said that Money also forced the children to take their "clothes off" and engage in "genital inspections". On at "least one occasion", Reimer said that Money took a photograph of the two children doing these activities. Money's rationale for these various treatments was his belief that "childhood 'sexual rehearsal play'" was important for a "healthy adult gender identity".