If I had to guess, I'd say this ruling was a result of having to work around age-old technicalities in state law.
It might be that a lawsuit against the parents would only be successful if the parent could be shown to be negligent. And, as this judge stated, the term "supervising" is just too vague to have any legal meaning. The judge, however, obviously does feel that the victim's estate should be able to sue for certain damages.
Being aware, as are likely the lawyers, that a negligence suit against the PARENT would be picked apart by opposing lawyers, the judge is allowing the child to be named as the subject of this particular suit. Remember, this would be a CIVIL matter, not CRIMINAL. They do not have to show that the child did this negligently beyond a reasonable doubt--they simply have to demonstrate that the child DID hit the woman, eventually resulting in her likely premature death.
The problem is that they're presenting it in the media in this way because 1) it's funnier and 2) it allows them to villainize the legal system. In doing so, they're allowing people to mix up the terminology and thought processes for civil and criminal law.
TL;DR: This simply allows the plaintiff to name the child in the suit, likely getting around a technicality that the opposing lawyers would exploit if the PARENT were named instead.
The payoff: The money will still come from the mom. Also, I'm not defending the lawsuit itself, but simply saying that (while there are many examples of the failings of our legal system, this isn't one, it's simply being presented as one).
