It's a problem on so many levels.

We've probably lost the fight over GenAI marks, at least for now, and I do understand the need for them. However the same technology that can embed an invisible watermark that survives a round of photographing, printing, crumbling and scanning back - can be used to embed more information than just "it's AI generated". Encoding GUID is just a harbinger; as a next step, why not encode the app that produced the image? Also a hash of its license key? Hell, what's stopping an app from doing it itself, watermarking its own window before passing the pixels to OS for compositing?

"Robust GenAI watermark" today is "robust general-purpose DRM watermark" tomorrow :).