Author's argument is that when early humans painted, they weren't expressing an interiority they already had; they were engaging the creative process of reality directly.

I disagree in the sense that reality includes the intangibles which machines cannot (today) reach, which is why any LLM-generated art is, for the most part, not art. It's images, it can be aesthetic or narrative or whatever – but I think it's fine to gatekeep art as an inherently human thing.