Oh dear, the level of ignorance shown in the comments is profound. This bit in particular is so worrying "Gender specialist doctors can tell the difference between a tomboy and a trans boy, or a feminine boy and a trans girl. They know how gender dysphoria presents in patients and how to diagnose it". That's completely untrue. I think this person needs to read Hannah Barnes's book.
It's worrying that they don't seem able to understand that Willa is only 'living as a girl' now because he's playing out stereotypes, the existence of which is hugely damaging for girls and women but also for men. It's offensive to hear anyone of any age say they're 'living as the opposite sex' when what they mean are the fripperies and finery which has been used to subjugate women for centuries. Willa obviously is child and should not be held accountable or what others are doing to him but the adults involved in this are doing despicable awful things to children - not just the medicalisation of the 'solution' but also the entrenching of gender stereotypes and the complete inability to look beyond their own self interest and reflect.
There have always been people who say no to the gender stereotypes. That I will celebrate. Pretending people change sex? That is not for celebrating. It's a sickness and if not in the person then in the society which makes people think that to be themselves they need to alter their bodies.