According to the man that gave this talk, we don't need to worry about whether it was possible for the Jonah story to be true (surviving in the stomach of a sea-going animal for three days without dying), it was true because God said it, and that's what proves it to be true.
So does that mean that there REALLY was a prodigal son, or a beggar named Lazarus who was taken up to the Bosom of Abraham, or that there really was a a real-life guy who was helped by a Samaritan? Or a mustard grain that really became the world's largest tree? Jesus said it, so it must be true!
This quote evidences a naiveté about literature....that a story must be historical in order to express truth. Admitting that a story is fictional, that there is fiction in the Bible, is somehow verbotten. But why? Everyone recognizes the parables of Jesus as fictional, as stories made up to illustrate moral points. That is no problem. But there is a strange reluctance to view Jonah (or other legendary stories in the Bible) in the same way.
In ancient times, there was no clear-cut division between fiction and non-fiction (as the Library of Congress, for example, maintains today). Even historiography contained passages freely written by the author (such as speeches) which represent what the author wants to attribute to the figure, or represent the point of view of the figure as conceived by the author.