I really doubt that the Ice Age travel bureaus were pushing trips to the highland caves. It is far more likely that the people of the plains simply died off, and the only survivors were those accustomed to the cold weather. So the statement “flocking to caves in one of the most inhospitable parts of the continent” is either naive, or misleading.
Article makes a couple assumptions.
Different time, different climate. Might not have been anywheres near as windy then.
Any coastal settlements would have been inundated by rising sea levels as the the ice age ended. It is likely that the continental shelves contain a wealth of such material, but it is all under water now.