a tool for what?
I am adding too many comments to this board, and will try to shut up, but I HAVE to say one more thing about this "stages" thing. Stages are a tool you say. A tool for what? Merely a tool for understanding the mental construct of the writer who describes the stages in the first place! "You say there are stages to this writer's work. I see what you mean!"
These constructs can be very appealing. But understanding them helps us understand the mind or method of the writer who describes the stages and not necessarily the "true" meaning of the artist the writer is trying to explain. Does that make sense?