Jack99 hit the nail on the head.
James is trying to say "In a conflict between the rules and making the game fun, go with the latter" Put another way "Don't let spells or rituals run amok in your game and ruin the fun".
What he ended up saying is "DMs, feel free to cheat if it's in your best interest to do so."
11 pages later, I'm sure James would want to take that paragraph back for another shot, but its too late now.
I brought up an example earlier in the thread of ruining a murder-mystery story with Speak with Dead. Now, a good DM knows to rig a corpse so that it knows little. But every once in a while, a PC asks a question so out of left field, the story would be given away by its answer.
Do you answer truthfully? Not the corpse, YOU!
If you lie to preserve your story, are you now screwing your players out of an easy (but well-thought) victory?
If you tell the truth, your adventure goes form a long detailed mystery to basically two encounters (talk to corpse, go get the killer). Big adventure ruined.
Replace speak-with-dead for nearly any divination, it doesn't matter. It goes back to my question, is gentle rail-roading (even if it means deceiving your players to keep them from ruining the ending) acceptable if the greater good is a more enjoyable play experience, or should the PCs succeed if they outthink the DM?
I guess I'm blessed to have a group that tends to be more forgiving. If the latter situation happened (a truthful answer leads to an instant resolve) my players would be upset, so they'd rather me change a few details to keep the story going than have a cheap unsatisfactory resolution based over an 8th level ritual/3rd level spell.
YMMV, of course. Poorly worded paragraph, but the advice isn't a terrible as some people say it is.