There was just one thing. Although he did all of the thinking preparation, he had yet to write anything down. He claimed that all he had to do was type up what he was thinking. End of story.
The act of writing is an act of discovery. Thinking and planning are vital for successful writing, but so is writing and rewriting. Putting words to paper (or screen) is a process unto itself. You make a commitment to the process in a way that will shape and reshape your original thoughts.
Just as acting is reacting, writing is rewriting.