I disagree. I consider it very likely that the story originated as an explanation for why the Chosen People's lives were so hard if a tri-omni God ruled the world. Shouldn't good and loving god that knows and can do all have created a paradise for them? The garden myth was likely written to explain this. Why would a good God do that to them? They must have deserved it. Let that be a lesson to obey the Hebrew priests when they tell you what God wants you to do.
Many of the myths can be understood this way - the ones that have God punishing man for some behavior. The Tower myth is easy to explain why people speak mutually unintelligible languages. Can't you just hear the ancient Hebrews wondering why God allowed that? Man reached too high and needed punishment. Sodom and Gomorrah were likely destroyed by a
meteor, and obviously that was a punishment from God for something. The flood myth likely originates with the discovery of marine fossils on the highest mountain tops. Imagine the ancients scratching their heads trying to figure out how they got there. Only one answer was possible: the mountains were submerged - all of them - and only God could do that, so why? Man must have needed more punishment.
Why do you suppose the Hebrews added a timeline to their creation story? It depicts the deity as needing most of a week to create and then a rest. Odin and Tiamat didn't need a week or a vacation after creating their worlds. Why do that?
I'm guessing that that was added later, after the nomadic Hebrews became civilized. Who benefits from the advent of the work week with a weekend free from labor? Suggested answer: the priesthood and the collection plate, a consequence of settling in large communities with a central synagogue that people need to travel to rather than wandering as nomads, to pay rather than just feed, and to build and maintain the synagogue, none of which would be relevant to nomadic peoples.
As for metaphor (and allegory), these are literary forms with criteria just like a haiku or a limerick. Metaphor and allegory involve substitution of a symbol for something known. When he calls her the apple of his eye, the apple is her and he knows that. Likewise with allegory. It is fiction with a substitution of invented characters and events for known historical characters and events. Gulliver's Travels is a political allegory in which fantastical fictional characters substitute for prominent historical figures like Walpole in the British politics of Swift's era, symbolized by the rope dancer Flimnap. We know what these things stand for as did their author, and they are specific, not place-holders for what is not known. That's not what these myths are. They are erroneous attempts to explain the reality the mythologists found around them.
I think that the reason that such language is eschewed by believers (and even many unbelievers who esteem myths) is because the word allegory implies that the authors had knowledge of the actual historical event as Swift did when he wrote Gulliver's Travels, and really don't want to use language like wrong guesses, but that's what these myths are - wrong guesses taught literally explaining observed reality. Many are reluctant to use the word error with scripture.