Some video console games have books to explain every nuance. Some of those guidebooks were a hundred pages of screenshots, items and dependencies, saved checkpoints.
There are plenty of free online rulesheets and videos. PAPA with Bowen, has hundreds of how-to & strategy for most tables found in tournaments. How would you document strategies, certain goals, some with no particular order, the risk/return tradeoffs and would you need a simple, advanced, and wizard sections based on skill level.... that creates dozens paths to follow, depending on how well you could play. I don't think a single manual would do it given player skill ranges, you want the rules for casual or tourney risk/reward , points or story progression?
I loved JJp's map of goal paths seen in-game via status report- for WoZ, there are mini-mode qualifiers needed to melt the witch, the entire set of 8 diamonds to reach the grand wizard mode SOTR. Best of all, its highlighted of where/what you've completed in-game. Does it tell you in what order or what to stack? No.
So given the variety of audiences, and taste for detail or summary, etc. we have forums. discussions change with new code, strategies, videos etc.
I think Stern leaves it vague on purpose for many reasons. Perhaps #1, you can't please everybody - let them find their own way to play.