I would argue that Picasso's life experiences, the environments he grew up and lived in, the people he interacted with, and the world events that took place in his life (like the world wars) were the external developments that led to the development of cubism. Sure, an AI could take in and analyze the works that existed prior, but it couldn't have the emotional reaction that occurred en masse after WWI and started the breakdown of more classical forms of art and the development/rise of more abstract forms of art.

Or, as the kids might say, AI couldn't feel the vibe shift occurring in the world at the time.

Of course Picasso's life experience influenced what he chose to make. This isn't what the parent comment is talking about.

The claim was that current LLMs (though I assume they meant generative AI in general, since we're talking about image generation rather than text) are unable to produce anything novel. Meaning they either don't think Picasso's work is novel, or they don't think a human could have prompted an AI to make a new type of abstract art before having trained it on it. Whether the AI would want to do this is irrelevant. AIs don't want anything. They do what a human prompted. And while WWI may have shaped Picasso, learning data from WWI isn't necessary in order to make a cubist painting when prompted to stitch multiple perspectives into a painting. It's blending perspectives that are available from old data. And blending things in a new way is novelty. Most novel art falls into that category.