Is this a walkthrough or a game design document?
As a walkthrough, it is nice. But as the foundation for the game designers, it would be a fun because it is so lighthearted.
Looks like Tom Schafer style; I find him whimsical and funny in all of his communication. I don't think it's a stretch that this aspect extends to nom-public communications.
It's a game design document.
My guess is it is kinda like a first draft that some higher ups approve and budgets and then dialogue and game development and puzzle testing can begin.
Looks like a GDD but just for the puzzles, a PDD
Design document, from the page that links this pdf (http://gameshelf.jmac.org/2008/11/grim-fandango-puzzle-desig...):
"Tim Schafer at Double Fine has posted the puzzle design spec for his classic adventure game, Grim Fandango. It is that game's tenth anniversary; it was released on the Day of the Dead, 1998."