Good question, and one I suspect has been discussed, but will take a stab at it. Of course, understand that we as moderators are really just offering our personal takes on it. We volunteer primarily to act as bouncers to keep things civil and on the rails, and do not determine the content on the forum, or the views of Biologos.
That said, I think the human author of Exodus probably did believe in a 6 day creation, but that the Sabboth was the topic of discussion, not the length of creation, so making it about the length God took for creation up to the time of Adam is to make it something it is not. Certainly, God could have created at once in one instant or one word, but he did not. He related 6 days of work and a day of rest for our benefit and to set aside a special time and space to honor and worship Him.
Also, it actually does not say 24 hours anywhere. I’m sure the human author would not even know what an hour was. It speaks of mornings and evenings in Genesis, even before the sun was around, by which we now define morning and evening, as well as how we define the length of days, being one rotation of the planet in relation to the sun.
I hope that helps. What do you think of that? Any questions that that brings up, or problems that we should further consider with that approach?