I saw this and a phase does not last 6 years. Fair enough if you don't want them making the decision until they are 16, but at least let them delay their puberty until then! I can't imagine how awful it must be to know that you are one gender and have to go through the puberty of the opposite gender. And while I agree that at that age I could not have made an informed decision about my fertility (though I never thought about it, it may have been different if I had to think about it), I KNEW that I was female and if someone had tried to force me to go through male puberty and live as a boy, I think I would have really suffered.
If one of my daughters came to me and said that inside they were male, then I would do anything to make them happy. I don't think these parents have made these decisions lightly.