Because its got wizards and makes a lot of strong claims, including about wizards, that aren’t corroborated NY actual real historical documents, which we have for some of the times and places mentioned, including the Roman empire, who kept absolutely fucking anal records-in fact, when it split, we literally still use the word for half of them (byzantine)as the word for ‘absolutely fucking anal retentive bureaucracy’.
Youre working with more literary analysis and like ‘oh hey here’s an accurate description of an eclipse, so this person probably saw one, they were in this part of the world, so we can guess when it was written’ type stuff than historical details. An ancient stone dildo tells us so much more about a culture than your book about wizards.