If you actually self identify as non binary, what are you really saying?
Obviously you don't believe there are just two sexes, male and female, as otherwise you would agree that you are whichever sex your body actually is.
But if you believe there are several genders then you can't be non binary because genders are not binary.
I think that if you say you are non binary you are, by default, admitting that there are just two sexes and you acknowledge that you are one of them.
So how is any of that part of being transgender?