f: JW believe that and personally conclude that on their own.
very few JWs would come to the wt beliefs on their own, they are led carefully into the trap of controlled thinking. It is a circular argument to try to will the truth onto a matter by the delusion of so many. and dont counter with wt's "mental picture" explanation. no high mountain required, can be done in the basement.
coming back to the OP. the "Flood"
Jesus, the son of David, endorsed that event, by making it a parallel to the coming end. As a co-creator of the Universe and its laws and a carpenter, he must have known, that a small family business, using bronze age tool, could not possibly have constructed a vessel this size, Able to carry that full load, withstand for 9 month the immense stresses of rain and currents that swirled, rose at 10 meter an hour for 40 days.
It was time to set the record straight, not dignify a fable with the mantle of scriptural truth, absolute, unquestionable facts. ditto
The Messiah's conversation with Satan, the flat earth advocate, showing all the Earth's mighty kingdoms, far away. on a clear day, from a high mountain. It was time to give satan (and bible readers) a lesson in spherical geometry, dispel the error, the adversary's
false promise based on a fallacious premise. so,
yes wt, like some bible writers will equate their pronouncements with the word coming from god, them being that god, always at the disadvantage of the duped.