Calling it Child Sexual Abuse Material is doing exactly that.
That is what is depicted, that is what has taken place to produce the material. It puts front and centre that this is abuse, categorically and by definition, not 'porn'.
Why would that not be "porn"? I would define that as "material intended to sexually arouse the particular audience". Merriam-Webster appears to largely agree
The material being harmful and produced via abuse doesn't remove it from that definition, in the same way that rape isn't removed from the definition of "sex"
‘Porn’ these days generally implies legal and consensual. Reflect as you will on what that means about society and the pervasiveness of porn as compared to a few decades back.
Regardless, calling it CSAM puts the abuse aspect front and centre, and puts it in a separate category to that, it avoids euphemism rather than adding to it.
That is what is depicted, that is what has taken place to produce the material. It puts front and centre that this is abuse, categorically and by definition, not 'porn'.