(outdent) How about looking at it like this. RPG rulebooks are just that. The rulebook explains how to play the game, but it is not the game itself. The ISBN manual you reference below supports this; games "SHALL NOT" be given ISBNs. There may be some confusion in the matter, but one good example is found by harking back to AD&D; 2nd Ed. To play that game required (it being rules heavy, that really is pretty much true) a minimum of two books—the DM Guide and the Players' Handbook. Neither "contained" the game, and the game went far beyond what was in either. The game in all its entirety encompassed the contents of many books, magazine articles, supplements, pamphlets, online articles and what was in the head of the players. The book is about the game; it is not the game.  

For that matter, a number of the articles you tagged did not list an ISBN, so you can't really claim that you claimed it was a book in ignorance because of the ISBN. A publisher doesn't mean it's a book, as board games, computer games, and any number of things are published and have publishers.