They specifically called it “child abuse content”, not “child abuse”. This seems perfectly valid, no?
By the way, just because these are digital renderings does not mean that there is no harm. Seeing such content can still be harmful to past victims. Just try to put yourself in this situation: imagine just playing some video game online, and suddenly being exposed to people recreating traumatic experiences from your past. Not only that - you also discover that the creators of the video game are involved & actively enabling such content. Seems completely messed up to me.
Good luck with the upgrade!
You can check the federated/defederated instances for any instance on the /instances page. For example:
https://sh.itjust.works/instances
https://beehaw.org/instances