That is not exactly true under US law. You're simplifying what the copyright office has said to the point where you're missing the key points of what they were trying to convey.

The copyright office has affirmed multiple times that whether or not you use an LLM is irrelevant. Copyright eligibility requires "sufficient human-authored expressive elements". It doesn't matter what tools you use -- an LLM, a troop of trained monkeys, etc.

Ultimately all that matters is whether or not the human creativity involved qualifies. Because copyright is ultimately a right that protects human creativity.

So yes, if you put "write me a book" into ChatGPT -- that clearly does not quality for copyright. "Write me a book" itself is not creative enough for copyright.

Now on the other hand, if you spend 1000 hours writing a book, and you run it through ChatGPT for suggestions and/or edits -- there is no reason why that LLM output would not qualify.

https://www.copyright.gov/ai/Copyright-and-Artificial-Intell...

It varies a lot in other countries, but in most (if not all) an AI cannot hold a copyright.