"Believing in Christ means believing in what He said. Do you contend that Christ did not believe the Genesis account of the Flood?"
Christ told parables to teach spiritual lessons. He alluded to things the people of the time would understand. I doubt if Christ (God) thought all the animals floated around on a wooden boat for a year or that it was necessary.
Another explanation is that someone else said this and it was attributed to Christ.
The alternative that Christ believed in nonsense is untenable.
What is your definition of nonsense? Does the physical resurrection of Christ meet the requirements of your definition of nonsense?
Excellent point.