It’s not incorrect language, but it is a deliberate choice to use language that minimizes the offense. They could describe the victims as children , teens, minors, girls, etc. They are deliberately saying “underage woman” instead of “15 (or 13) year old girl” because their editors will pull it for being too inflammatory, sensational or unprofessional (as if that is a regular concern in the modern press).

A similar thing happens when the police kill someone. All of a sudden all of the rules about using active voice for good writing go out the window and it’s “man dies in police involved shooting” rather than “Police shot man.” People who study journalism and writing in school and are full time career writers and journalists absolutely think about word choice so I have a hard time believing that this is accidental.