It surely is, but that doesn't change the fact that many cases are not about distribution and the harm is frequently more of a legal fiction, unless by harm you mean something other than suffering inflicted on the victims. I don't necessarily think it's wrong for society to ban certain acts on purely moral grounds (another example: incest between siblings), but let's not pretend it's something else going on.

> Non-consented distribution of sexual images (eg: revenge porn) is also a crime.

There is very compelling empirical evidence that this causes actual harm (suicide ideation in a very big fraction of the victims), even if it is fictional, so here there is no question about the harm.