I think you might be overestimating how common your opinion is. In many (maybe most) countries, children are considered capable of consent even before they are granted all privileges of adulthood. Sometimes it's only if the partner is underage as well, but then one will be an adult sooner than the other, so there are exceptions for cases where the age difference is small.
Because of the various exceptions in traditional consent law in contrast to bright-line rules against child pornography (below 18 is illegal, no exceptions), it's possible for legal sex to become illegal as soon as there's a camera between the participants.
The best-known cases are probably of teens being prosecuted for child pornography when they take nude selfies.
What you say is true for interpersonal relationships. The article is about imagery with an erotic element. So in the context of erotic photography I think that most countries would consider participation of children illegal and I think most people would agree with that.
So I'd think that in the context of the article it could be a pleonasm, but an understandable one then.
I think you might be overestimating how common your opinion is. In many (maybe most) countries, children are considered capable of consent even before they are granted all privileges of adulthood. Sometimes it's only if the partner is underage as well, but then one will be an adult sooner than the other, so there are exceptions for cases where the age difference is small.
Because of the various exceptions in traditional consent law in contrast to bright-line rules against child pornography (below 18 is illegal, no exceptions), it's possible for legal sex to become illegal as soon as there's a camera between the participants.
The best-known cases are probably of teens being prosecuted for child pornography when they take nude selfies.