It's missing random flaws. Often the noise has patternd as a result of the diffusion or generation process.

Yeah, I was thinking about this. Humans vary depending on a lot of factors. Today they're happy, tomorrow they're a bit down. This makes for some variation which can be useful. LLMs are made to be reliable/repeatable, as general experience. You know what you get. Humans are a bit more ... -ish, depending on ... things.