Earlier quoted context omitted.
They're the same thing and used interchangeably. The sexual abuse is from the sharing lascivious pictures of someone taken without their consent, with the additional context that children are not understood to be capable of consent for sharing lascivious pictures. It is not physical abuse.
That... is an abuse of the word abuse. Also wouldn't that logic apply to pictures that were originally taken openly and innocently?
This does lead to poor policing (like the famous Google banning man for taking photo of his child's genitals to send to doctor story).
It appears that in present-day English people use the word 'abuse' to mean more than physical abuse. If you're a prescriptivist that may upset you, but isn't that the nature of being a prescriptivist? Does it perhaps beg the question "why be a prescriptivist?"? Aren't you, perhaps, literally standing against the world?