I mostly agree about the justification in the repo being wrong, but wanted to engage about this point:
> Image generators cannot insert watermarks into things they did not generate
It's actually very easy to take a real image, ask Gemini/ChatGPT to modify some tiny part of it (could be something as silly as lighting/shadow/etc), and often the resulting image will be detected by their watermarking tools. This way you can easily present any real image as AI-generated.
So what? I can also open an image in Photoshop and make sure it saves out some Photoshop specific EXIF data and try to claim the image was doctored. What I can't do is go and put my deceptive altered file up in place of the original in all the places on the Internet it exists.
Ignoring that a watermark removal tool does not help with this threat model, the claim is still true: the original image can not be changed, and instead a copy is created.