> It's a weird fact claim, because the ground truth is "nobody knows for sure" and that's not one of the available options.

It's even weirder to suggest that the disagreement is indicative of a problem. If you asked five very knowledgeable humans on this subject to select the correct answer on a multiple-choice questionnaire, they would almost certainly vary significantly more than these 5 LLMs.

Not to say that hallucination isn't a problem, but this is a lousy way to test it.