Where I used to live, I noticed an optical illusion. As I was walking, there was a clearing ahead of me with a spectacular mountain view. In the foreground were two hills. One partially obscured the mountain, although the mountain towered above it. One hill was directly in front of the mountain while the other was alongside the other hill. Looking through the dip between the two hills, you could see some foothills of the mountain in the background. The foothills were blanketed in snow. The hills in the foreground had no snow. Yet they appeared to be about three times higher than the snowy foothills in the background. Therein lies the paradox: how could the foothills have subfreezing temperatures when they appeared to be about two-thirds lower in elevation than the hills in the foreground, which were dry?
The explanation, of course, is that relative distance generates an optical illusion. In reality, the foothills in the background are far higher than the hills in the foreground. Probably above the tree line.
Now I say all that to say this: unbelievers infer from certain passages that Scriptures asserts a flat earth and/or three-story universe. Inerrantists counter that this is a phenomenal description.
By the same token, young-earth and old-earth creationists debate how to construe geographical markers describing the extent of the flood. Old-earth creationists say that's phenomenal language.
There's nothing inaccurate about phenomenal descriptions. That depicts a scene from the sight-lines of an observer. And that's how it really looks from his vantage-point.
Spacial descriptions always have some frame of reference. They implicitly have an indexical perspective, even when they are expressed in third-person terms.
Likewise, the original audience for Gen 6-9 certainly had a difference sense of world geography than modern readers do. How they'd correlate those descriptions with their own sense of world geography doesn't correspond to a modern reader's default frame of reference. So we need to be on guard in that respect.
The larger point is that we'd expect a historically accurate, eyewitness account to have phenomenal descriptions. That's not erroneous–just the opposite. It is, to be sure, a somewhat provincial viewpoint. Yet that's the nature of firsthand observation.
But my example illustrates the how easy it would be to draw fallacious inferences from phenomenal descriptions. That's something we need to guard against.