It seems complicated, and I have never felt like it was more than a model. It appeared in the heyday of evolutionary theory. The idea that scripture could evolve is an interesting one, but I just don't think we can track the original sources with word studies. Nobody seems to be tracking the evolution of the ideas in the Bible. I note that Karen Armstrong's book never mentions any of the concepts in the surrounding cultures how they may have influenced the Bible or contrasted them. Where could Biblical ideas have come from? Noah's story looks a lot like Gilgamesh's story but the ideas are opposite. The results are opposite. Noah doesn't evolve from Gilgamesh nor Gilgamesh from Noah. The concept of evolution breaks down. Maybe we can track original sources but not without tracking ideas. I'm not getting it.Contrary to the belief of some, the Documentary Hypothesis has not fallen out of favor but instead been added to by some other hypotheses. typically based on oral traditions being passed on down. The idea that Moses wrote the Torah has been discounted by biblical scholars with the primary exception of those within more fundamentalist denominations. There simply is not one shred of evidence to support the concept that Moshe wrote them all.
I hate hearing concrete assurances (not by you but in general) that we now know how the Bible evolves. We don't. We are still learning things about the cultures in the Bible.