They do. And they're not 'abnormal'. When it boils down to it, who really is entirely normal, and what does normal mean, anyway?
But these days there's no mutual exclusivity between dysphoria and transgender. There are other factors it's vital to consider: the correlation between young girls, ASD and transgenderism being one. Another is the devastating Cass Review of the frighteningly inadequate, frankly dangerous practices being operated by the Tavistock, and a growing (and alarming) trend toward medicalization as a first resort, and with no follow-on care or monitoring of the medium-term wellbeing of those patients. As for Mermaids, anyone with a genuine concern for young trans people would be rightly horrified by some of their rhetoric, not to mention the way they operate and the known predilections of one of their trustees.
The whole thing is a can of worms and to accept it uncritically is, IMO, to do young people a grave disservice. To this end my Y6 child knows that sometimes people choose to present as a different gender, and they should be free to do so and don't deserve to be discriminated against. They would, however, still be the same sex they always were; yes, that would still be true even if sex isn't as straightforward as it seems (albeit straightforward enough for homosapiens to have survived for 200,000 years). Sex is not 'assigned at birth'. Humans cannot change sex.
DC knows these are basic rights to which every human being should be entitled, but is too young to understand the complex issues surrounding what happens when the rights of two groups conflict.
There's also a false dawn (to my mind, a cruel one) in assuring a young person with complex problems that they'll suddenly find happiness and a miraculous solution to those problems by transitioning. To transition is not to guarantee happiness. The testimony of a growing number of detransitioners bears witness. to this