Personally, I think the creation story in Genesis is a much simplified version of the actual events. Imagine, if you will, that you were trying to tell a six-year-old how television works. You might be able to cover certain technical aspects, but you would of necessity have to considerably simplify many aspects and use metaphors to describe others.Sure, but would God explain the Big Bang & evolution by way of the Genesis story? If I were God, I'd come up with a better, yet still simple, explanation of how I created the universe. Something about how I started everything in motion, giving the elements the ability to combine in a myriad of interesting & unpredictable ways, and living things that had the ability to change over the generations & morph into countless interesting & unpredictable genera, families, even kingdoms - all for my amusement. Finally one such type of living thing developed into a species with the ability to think about these things, and now I get to have a relationship with you. When that happened I was happier with my experiment than I ever thought possible! In fact, I now consider you my children, and I want you to live in peace & harmony... Hey you, stop killing your brother! Hey, I'm talking to you! Stop that right now or I'll end this experiment RIGHT NOW. Do you hear me???Compared to the mind of God, the mind of Man is nothing--the difference is far greater even than that between an adult and a two-year-old. The Creation Story must almost certainly, then, be a considerably abridged and simplified version of actual events since I don't think the mind of man could fully comprehend what really happened.
Well, something like that.
The thing about your explanation I really don't agree with (and it's a popular one in apologetics) is that God wasn't trying to explain cosmology to six-year olds. An adult from 6000 years ago may have been much more ignorant about a lot of things than we are today, but he was still an adult. God shouldn't have to make up children's stories to explain this. He should be able to come up with a simplified, yet straightforward, explanation.
In fact, if He had given them an explanation with parts that wouldn't get completely verified until much later, that would be even more compelling. Similarly, if He hadn't created all those beams of light already in transit to Earth from all those zillions of brand-new stars, we'd see more & more stars blink on every year, and that would be compelling evidence that the universe really is only 6000 years old.