Not a very good argument. It is easy to understand why we know that there was no flood, if one can be honest.
Luckily for you Jesus also used all sorts of tools of tale telling, allegory, parable, etc.. Claiming that Jesus believed the Flood myth is akin to claiming that Jesus was not divine.
A fragment from the Epic of Gilgamesh has been found on a clay tablet at Late Bronze Age Megiddo, so the story was known to the Canaanites who had scribes trained in writing cuneiform.
Of interest here are clay tablets from the Egyptian appointed mayor of Jerusalem called Abdu Heba found in the archives of Pharaoh Akhenaten in Egypt warning him all of Canaan has fallen to the Habiru and only Jerusalem is holding out and to send aid before the city falls.
We are told that the Jebusites lived in Jerusalem and that Israel intermarried with them.
Perhaps it is via Jebusite scribes trained in cuneiform that the Epic of Gilgamesh came to be later recast as Adam and Eve in Eden by the Israelite descendants of the Iron Age I and II intermarriages with cuneiform-literate Jebusites?
Did Abdu Heba come to have his name morphed by the Habiru into Jebus or Jebusites?