…and then we’re back at “someone can take that model and tag real images to appear AI-generated.”

You would need a closed-source model run server-side in order to prevent that.

I highly doubt any commercially available service is going to get in on officially generating photorealistic CSAM.

What would stop someone from creating a tool that tagged real images as AI generated?

Have at it with drawings that are easily distinguished, but if anything is photorealistic I feel like it needs to be treated as real.