Except it still sets a precedent with regards to non-photographic images - especially when it covers anime/manga.  By definition, the stylized characters are almost always possible (probable?) to consider as depicting "kids".

Don't get me wrong, when it comes to actual kiddie porn, the makers and possessors deserve to be taken out and skinned alive one cell at a time down to the bone - but this can still set up a bad chilling effect precedent.  Who really wants some faceless WASP being able to decide if the images they possess, ones they created solely in a computer, are by their definition "obscene", and they face a felony charge for the privilege?

You get asked if you've ever been arrested, and you have to say yes because it was something like this, and it was for "possession of obscene material", you're screwed - even if it was tossed out of court because the images in question were half-finished renders of figures you haven't put clothes to yet ... Not good.