A five-year-old also doesn't have any money of his own. Ultimately, the parents are spending the money and also the ones responsible for changing the situation.
The parents were most likely not aware.
Some platforms/games purposefully design their UX so that it's hard to control for a parent and easy to spend for a child.
If you're not aware of 6k charges on your credit card (or even 6 dollars) then you're a very, very irresponsible person, let alone irresponsible parent.
So your child spent 6k$ and you are now aware of it. So what? This article specifically talks about the employees who talk about child as whales when discussing whether to refund or not. Presumably the 5 year old kids did not request the refund themselves.