>Why is an anodyne factual claim an “extraordinary claim”? What makes that particular claim extraordinary?

FWIW I tried to get AI to substantiate it and came up empty. Maybe it's not as "extraordinary" as "Obama was a reptilian alien" or whatever, but for everything else what counts as "extraordinary" depends on your prejudices, I suppose. Regardless of whether it's "extraordinary" or not, it's definitely not common knowledge and needs to be substantiated rather than asserted without evidence.