Yep, my understanding is that many guardrails like this are actually the result of government legislation (eg the Fable bans) or terms of settling copyright lawsuits over reproducing copyrighted text and lyrics.

I mentioned it in a sibling reply, but here's Anthropic's support document about not using Claude to reproduce content verbatim that already exists, regardless of copyright.

https://privacy.claude.com/en/articles/10023638-why-am-i-rec...