Not everyone involved does not know what they are doing. The dsm5 website has summaries in the changes. On the one for paraphilic disorders, one of the conditions that can (along with other factors) get you labelled with a paraphilic disorder is a "desire for sexual behaviors involving unwilling persons or persons unable to give legal consent." Although that differs from what the actual DSM-5 section on pedophilia specifically says. Still, whoever wrote it recognized that the DSM-5 was basing disorder vs non-disorder based on legality to some extent.