Okay, the novel No Time Like the Past by Greg Cox is not considered canonical, as much as I enjoyed it, so the events as depicted there should not be taken into consideration. As to the rest, all we have is Bele and Lokai's word about anything considering the people of Cheron, and they were gone for 25,000 years, so their information could be a little out of date and should not be considered as absolute proof. It is not hard to surmise that some natives of the Cheron population decided to leave the world before it's destruction and settle elsewhere. It doesn't contradict anything, it just brings in information that we didn't previously have.
