A 4 year old son live as a girl

This is a bit confusing to me so decided to bring it here so we can talk about it. Is there any way a 4 year boy can know without any doubts that he wants to be a girl?

Kathryn and Jeremy Mathis have five children, including a set of triplets, one of which is a boy named Coy. Now according to Kathryn the mum, Coy, who loves pink, began gravitating toward girls’ toys and clothes by 18 months. Gender eventually turned into a bigger issue when Coy asked, at age 4, “When are we going to go to the doctor to get me fixed so I can be a girl?” A psychologist confirmed then that Coy was indeed transgender, at which point the parents decided to let ‘Coy be who she was.’

Coy at 6 years old is now living as a transgender. The problem now is that Coy has been banned from using the girl’s bathroom at her school, and the parents have filed a formal discrimination complaint against the school through the help of a lawyer. The parents are fighting for her right to use the girl's bathroom, but after all said and done, he still has a penis.

So if my 4 year old boy loves pink, says he wants to be a girl, I will let him live as a girl? Why not wait till he hits puberty to see if he'll grow out of it? Is it not too early to be slapping labels on kids, especially ones that carry such life altering meanings?