My cousins were at least 5'10 when they were 13 years old. Now they are at least 6'0. When you are taller and stronger, it's easy to attack. Even easier if the girl was petite.
I am surprised they released his name and photo. There have been quite a few violent/sexual attacks on children by other children in the UK and their names and photos have not been released. So yeah, I find it strange they released his i.d.
They do sometimes in exceptional cases such as little Jamie Bulger killers..