Definitely open to the idea, that couldn’t be the whole argument. I mean, my brain can output some quotes, but I’m not a compressed storage algorithm. Or at least I hope I’m not.

I've seen examples of this, but they're nearly always isolated, rather difficult to obtain, and not in fact exact copies. You need to specifically ask for an exact copy, and then attempt to defeat the safeguards the model has in place to prevent this, and hope that it was "memorized" - which for the record is considered to be a flaw in the model as it's a reduction in information density and capability, compared to if that "memory" was used for something else. Good models seek to reduce this as much as possible. With the size of the datasets involve (see OP) this feels more like an understandable and reasonable issue to have.

This very rarely happens, usually when trying hard to get it to regurgitate, and I don't think it has ever happened for anything longer than 2 paragraphs, or at most a short article. Certainly not something like a book or even the whole issue of a newspaper.

Yup, exactly. Passages from GoT appear because they're frequently referenced across the Internet, including the multiple wiki style sites for GoT fans, not necessarily because the LLM is regurgitating whole-book content it was trained on.