> They can and do say "I don't know".

Parent poster never claimed they couldn't generate the text of "I don't know."

But when an LLM generates "I don't know", it does so with the same mechanics that lead it to "My foot hurts" or "I miss my deceased grandpa."

They're all lines for a fictional character within a movie-script (or chat-transcript) that was repeatedly run through a Make Document Longer algorithm. Each of them needs to be approached with an identical level of context-awareness and skepticism.