Do you really not realize how nonsensical this reasoning is? Did God reveal The Iliad to Homer, just because Homer could not possibly witness The Trojan War himself?
The universe was not created from primordial waters, there is no firmament, stars are not just lights in the firmament, there are no waters above firmament etc. What do you mean by "such knowledge"? There is nothing supernatural about it. It is actually scientifically incorrect.
It is mythological drama (Gen 1) and mythological narratives (Gen 2 and next). Such genres were common in many nations - Sumer, Egypt, Babylonia, Persia, Greece, Rome... and of course in Israel.
The purpose of Genesis is theological and nationalistic, not scientific. It was not even written at once, but had multiple authors and composers.