To be fair, that's a very hard connection to break because it is just everywhere and still gets repeated as gospel. But it does make a lot of sense when you think about it. There are many more opportunities to identify an internal feeling like one's gender identity than there are for something external like who they may be attracted to.

I myself knew that being a boy felt wrong as early as 10. I'd had some run-ins with that feeling before then because of the way my father treated me. Things like getting berated for being too emotional, and him getting rid of a baby doll that I carried around and took care of when my Mom was doing things for my baby brother that I couldn't help with. With the stated reason that he didn't want me to grow up to be some kind of queer (though the word he used was much worse). But 10 is where I first remember recognizing the feeling of my body being wrong.

Of course I didn't have the words for it at the time so I didn't know what I was experiencing was dysphoria. Nor did i know that nonbinary was even a thing you could be. I understood that trans women existed, but no matter how hard I thought about it over the next few years I didn't feel like a girl either. It took until I was 26 before I finally realized with the benefit of hindsight that I'm nonbinary. So I'd already been forced into a male puberty which hit me like a train. I'm 6'2" (~188cm) and built like a balding fridge in a fursuit. I'm almost 35 now and because of other medical issues I haven't been able to transition so it is very hard to not feel like it's too late for me even though I know it's not. Especially in the current political climate.