They’re not denying it was an event, they’re saying that there are historical indications that mankind was nearly wiped out. And that would correspond very closely to the Biblical narrative: only 8 were saved.
Let’s see... ark of Noah, saving mankind, comes to rest on the 17th day of the month of Nisan.
Joshua (ie, the name ‘Jesus’) leads Israel into the promised land on the 17th day of the month of Nisan.
Later, another Jesus rises from the dead, on the 17th day of the month of Nisan, saving mankind.
It all fits. (And there’s lot’s more.)
They’re hedging their bets. The Flood either happened as recorded in Genesis and latter affirmed in the NT or it didn’t.
Only 8 souls from the Adam.. There had to be other peoples surviving because we see them alive and well around the globe. Christ was to come through Adam and Eve... The devil did everything he could to pollute that bloodline. God left nothing to chance, He already had His plan and set it in motion...