Those are not new ideas. Those are based on persons experiences up to that point. There is nothing magical in human brain that we cannot eventually implement in AI.
And would you say that an idea formed from the combination of multiple old human ideas is not original? If the influence of an existing idea disqualifies it from being original then very little could be considered original. If something additional to existing ideas is needed for originality then that what is that thing which is beyond the capability of an AI?
Personally, I would argue that any new combination of existing ideas is inherently original (i.e. a fresh perspective.)
Talking specifically about image generators (rather than LLMs) which are trained on billions of images - some of which would be widely considered as artwork (old ideas?) and others documentary photographs.
How so? What is it that makes art OC that cannot be applied to AI created art? I think it would take an extremely narrow definition which would also exclude a significant amount of human created art.