This poem is primitive nature myth to explain earthquakes and thunderstorms. Noah may have known about the Zagros Mountains 110 miles east of Shuruppak. But since he could not see beyond the horizon, he would have no knowledge of whether the Zagros Mountains were flooded or not. He reported only what he could see and he could see only sky and water, because he was several miles from shore. A flood in Armenia 17,000 feet deep while Egypt or India were not flooded would be a more incredible miracle than anything implied by the traditional understanding of a universal flood.
Mountains is a mistranslation.
The flood covered hills not mountains.