Our society is pretty aligned that distribution is another kind of harm. Non-consented distribution of sexual images (eg: revenge porn) is also a crime. Children don’t need to be the ones to press charges in child porn unlike with adults. That’s a good thing.
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.
> Our society is pretty aligned that distribution is another kind of harm.
As well as possession. I don't actually know if those are different for CSAM, but I would assume so because they are for drugs.