>> No, that human owns the copyright on the prompt, not on the work product.
I think I may have misunderstood your original comment above. It seems intending to say:
No, that human owns the copyright on the prompt, not necessarily on the work product. The human may partially have copyright over the work product as well, "how much" being dependent on how much new creative expression from the human was involved vs that from others.
That is in fact correct.
Both the compiler (in absence of inclusion of copyrighted libraries) and the LLM are considered to not add creative work and thus do not change copyright status of the works they transform.
You can consider the training set of the LLM or other AI model to be 3rd party libraries and the level of copyright from them applying to final output to be how much can be directly considered derivative, just as reading copyrighted code and being inspired by it does not pass that copyright to your work unless it's obviously derivative
>> You can consider the training set of the LLM or other AI model to be 3rd party libraries ...
I like this comparison -- training set as '3rd party libraries'. Except, of course, that the authors behind the training set may not have actually granted permission to use, whereas the 3rd party libraries usually have some permission by way of license.