Figurative.
That does not follow. For example, if someone said, "I love you with a burning hot passion," would that be figurative or literal? Well, the "burning hot passion" part would be figurative. Does that mean that the subject does not love the object, and that he's lying? Of course not. Just because someone is referring to an allegory doesn't mean everything they say is allegory.
A literary allusion to a mythical trope in no means negates or invalidates the comparison. Authors frequently use allusions or comparisons, sometimes to true stories, sometimes to stories that are fiction rather than non. As long as the reader knows the original story, it doesn't matter whether that original story is historical or not.
Have you not ever compared something that happened to you or someone you know in terms of a make-believe event? Like, "Gosh, this is just like that tv show," or, "Hey, that's almost like the movie..." Your audience knows the tv show or movie in reference, so they can understand the comparison. They don't think that you think your life is actually a television show, or that you can't tell the difference between reality and fantasy. They know you're drawing a comparison, and if it's a good comparison, it will make sense to your audience, or will add something to the conversation.
Similarly, the audience of Exodus knows the Creation Story intimately, so they understand that when the author is referring to it, that's what he's talking about, and why. "Hey, even God rested, according to our Creation Myth. That means we should, too." The author is simply referring to the creation myth that he, and his audience, already know is a myth. Saying it is a myth is not saying it isn't "true." It's just not historical. It is most certainly true, far truer than anything science could possibly teach.
