Maybe he could look instead at the absolutely uncanny way the ancient document parallels, in a way that everyone can understand, what we know today about the sequence of events.
When I was in elementary school, one of the subjects we were supposed to be studying was transportation (second grade). For that segment of the morning, our teacher had us draw horses every single day for the entire year, except for the last week, when we drew pictures of chariots.
Same principle. It's a teaching method, one that puts things in their proper time perspective, or something close to it, in a way that you can never forget. Just as we need to remember for how short a time we had the wheel, much less the motor vehicle, we need to remember how short a time we have been here in the grand scheme of things. Imagine how confused people must have been before Genesis was written.
And how did the writer know this? Uncanny wisdom.
No need to postulate about light traveling at different speeds back then, for pete's sake.