I don't think I've seen the answer you're chasing.
I also don't have it but it's a very intriguing question.
My assumption is that it is just close enough and we based the amount we're meant to eat off of what worked and retroactively added the numbers in.
As for the interchangeability of it all, at the end of the day the body wants glucose ameno and fatty acids to make energy so it breaks things down into it. Most stuff is made of the same basic three building blocks.