I’m not convinced they didn’t have rights to those images.
“Millions of images” is not really a lot in photography as compared with, say, painting. I can easily come back from a weekend trip with several hundred shots. Even with digital tools, I doubt an artist can produce a comparable number of images in a similar time frame.
I was listening to an interview to a photographer who collaborated to an AI training project, and mentioned that he provided them with a catalog of ~ half million images he had taken over 10-15 years. And that ‘s just a single case.
I think a lot of photographers/studios/press agency have a backlog of shots that didn’t make the cut, but could still be useful for training something like a denoising algorithm, and could be convinced to provide them for a reasonable fee. After all, unused shots are basically a loss, and the end product is not something that competes directly with their work, but actually allows them to get better results.