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

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.