I cheated and just asked him. :-D
If you're interested, his response is here:
Ha! Well, that explains things rather neatly then. If he was really building only up to that final paragraph, it would have been shaped differently. Instead it seems that was just one conclusion he drew out of a project started for different reasons. Thanks for sharing this.
Since I'm interested in information design (especially right now) I was quite disappointed with the graph he ultimately produced. I'm hoping someone with a bit more time than me takes up his challenge and goes back to correct some of his mistakes (in both analysis and storytelling). I'd rather like to do it myself but I doubt that's going to happen anytime soon.
Ultimately, a compelling story about how we as humans require stories for understanding, and how important it is to verify the stories that we choose to believe.