I think she mentioned Mr. Atoz..
I'd have to watch the episode again, but I don't think Zarabeth ever once mentioned Atoz. (Spock uses the name in front of Zarabeth, though.) Besides, Atoz told Kirk they did not have much on recent history, "There was no demand for it."
Maybe the recent history, aside from being a poor destination for escaping the nova, was also the time of Zor Khan. What's "recent"? Maybe a generation or two? The lack of "recent" history may also be a technical limitation of the atavachron. Maybe it can bend time only so much, as "recent" history is below its horizon, so to speak, like the aim on a gun turret.
By the way, how did the Sarpeidons know their sun was going to go nova? They obviously have a time machine, but no spaceflight. So maybe someone stepped through into the future and got fried. We can only hope it was Zor Kahn.