According to Plato, Socrates himself defended "noble lie" as in lie that "to maintain social harmony or to advance an agenda".
Besides, "ancient historians" were not historians in our sense of the word at all, so I don't understand why are you asking for historian specifically. They wrote a lot of obvious myths (falus appearing out of fire) and there is no expectation for those texts to be accurate.
Ancient texts were written for purpose and with limited knowledge (just like any contemporary text) and it would be oddly naive to think anything else.
I'm asking if there are any instances where an ancient author is known to have lied about something that could be believed by a modern historian if they didn't know any better. For example maybe some Sumerian committed tax fraud on clay tablets, but we caught them thousands of years later. I'm wondering if any specific examples of that are out there.
Edit: to be clear, I'm asking for a specific example, not an argument that an example probably exists out there somewhere.
Besides, "ancient historians" were not historians in our sense of the word at all, so I don't understand why are you asking for historian specifically. They wrote a lot of obvious myths (falus appearing out of fire) and there is no expectation for those texts to be accurate.
Ancient texts were written for purpose and with limited knowledge (just like any contemporary text) and it would be oddly naive to think anything else.