The thing is that it's already illegal for minors to see pornography.It's not illegal for minors to access their technology devices or watch disturbing news footage.
This is merely an enforcement vehicle for rules that already exist. It is an acknowledgment that the law that has been in place for years doesn't work anymore.
Back in the pre-Internet days the adult video store or cinema would make sure you were of proper age to patronize those businesses. Sure, you could sift through your Dad's Playboys but essentially, an adult could reasonably be able to figure out how to limit exposure of content to their children.
In the current environment it's basically impossible.
An analogy to the status quo would be if drinking for under 21/18 was illegal but no bars or stores were required to check ID. That makes it effectively legal.
Now, as to your point on whether these rules make sense in the first place? I think we can reasonably assume that most of the voting public isn't in favor of legalizing pornography for minors. It doesn't really have to make sense when compared to other things we allow exposure to.
In other words, the existing laws already roughly reflect our cultural values. Most people in the Western world are literally more okay with showing their child something violent versus something pornographic.
If we all collectively as a culture decide to change that in the future, great, but I doubt a referendum to that effect would have majority agreement.
Essentially, the only concern with this law should be the anonymity of the age verification. All other concerns are addressed by the fact that a minor viewing pornography is already breaking the law.