> assumes AI ... are completely unable to synthesize new information out of existing information

I love it when we go back to assumptions. This is exactly what I'm assuming. However, the problem is not solved. what exactly is "new" information? here is more assumptions for you right there.

> Most humans works are derivatives of some other work

Good point. "Most", however, does not equal "All". collectively, we are not just copying. there is a newness. (again, what is new?)