That is the justification, yes. And it is impossible to tell whether there is a kid, an adult or a dog on my side of the tcp connection without mass internet surveillance which is the actual reason.
You don't need mass internet surveillance. You can simply restrict advertisement much further than today: the types of things that can be advertised, where they can be advertised, etc. We restrict all sorts of harmful activities, why not extend it to ads?
But that's not the proposed law under discussion, which instead limits the restrictions to children, menaing implementations of the law will need to come up with things that are convenient for the surveillance state.
Laws and law proposals can be changed. Hence my earlier comment.
Won't someone think of the smartphone addicted adults!