With respect the child in the article is not a girl.
Never was. Never will be.
And the people who have really let him down are his parents, teachers, doctors, counsellors, sports coaches and any other adult he has been in contact with who have failed, in the last ten years that they have had the opportunity to do so, to explain this to him. Yes, he might wish he was a girl, he might even have feelings for other boys which he , and possibly his parents, rationalises as normal boy/ girl feelings, but he is not, and never will be a girl.
Just as your child will never be a boy, much as they would like to be. Which means for example that they might be confused when they start looking for relationship partners and find that the people they are attracted to are probably lesbians looking for relationships with other women, not with people who say they are men. Or , more confusingly, heterosexual women who are looking for relationships with physical men , not other women.
You will of course have cautioned your child about the health risks of taking hormonal treatment, particularly devastating for women, with vaginal atrophy and early osteoporosis almost certainly guaranteed.
To be perfectly frank, and I am sorry if you take this personally, but imo by acting as a protective and supportive parent to your young child ( the motivation of which I do understand ) you might , for the sake of guiding them through a confused adolescence, have actually condemned them to a lifetime of physical poor health if they go down the surgical/ hormonal route.
I am sorry your child has been bullied at school and that they have not been better supported, whatever the rights and wrongs of gender confusion among young people, bullying should not be one of the outcomes.