Creator, or proof reader ?

It's not different - the output of an LLM may be a derived work of the original. It may also be a non-literal copy, or a transformative work, or even unrelated to the input data.

There's a lot of "AI bros" who would like you to believe that using an LLM automatically results in the output not being a derived work of the input, but this is completely untested in law; the current smart money suggests that "generative AI" output (LLMs, diffusion probabilistic models, whatever) will be treated the same way as human output - it's not automatically a derived work just because you used an LLM, but it could be, and it's on the human operator to ensure that copyright is respected.

It's basically the same story as a printer in that respect; if the input to the printer results in a copyright infringement on the output, then no amount of technical discussion about how I didn't supply the printer with a copyrighted work, I supplied it with a PostScript program to calculate π and instructions on which digits of π to interpret as a bitmap will get me out of trouble. Same currently applies to LLMs; if I get a derived work as output, that's my problem to deal with.

This, BTW, is why "AI bros" would like to see the outputs of LLMs deemed as "non-infringing"; it's going to hurt their business model if "using an AI to generate output" is treated, in law, as equivalent to "using a printer to run a PostScript program", since then their customers have to do all the legal analysis to work out if a given output from a prompt has resulted in a derived work of the training set or not.