It doesen't really look falsifiable to me. As a conceptual model it is certainly reasonable. It seems to fit all the available data. But so would a host of other models. You seem to be saying that it's reasonable that people may have thought like this, so based on that they may have concluded this, and therfore may have written this. Which is certainly reasonable, but I don't think really proveable one way or the other.
It's also conceiveable that the legends are basically true. Not literally true in every detail of course. But instead of invented myth that explains fossils, perhaps the flood legends are remnants and "theologised" (my made up word) versions of ancient traditions and stories about a real catastrophic flood. We know there was a period of intense, probably catastrophic flooding at the end of the last ice age. This was worldwide, and rising sea level must have affected all coastal civilizations. Abraham, coming to Caanan from Mesopotamia, was no doubt indoctrinated in the Sumerian version of the legend. Who knows maybe there really was some crazy guy who built a huge boat and put a bunch of animals in it. It could happen!