Sorry I was vague. I don't think that people saying "there is other information that provides some context" invalidates your issues with the passage quoted in the OP. But I do think that it provides basis for a larger point that the 4e DMG provides some very good, if not flawless, advice for DM's in general and new DM's in particular.
That point, when I read it strictly, is not really what I'm talking about AFAICT. Of course the "context" of my own post was the joking title of "part 1 of 1000" which would lead one to reasonably believe that I have 1000 things I don't like about the 4E DMG. One could readily, but I would argue not logically, conclude that I don't like anything in the 4E DMG.
There are a number of statements that you can make about the 4E DMG and they are not all equivalent to me, though they seem equivalent to other folks. One statement is: *there exists* bits of good advice within the DMG. This is different than statements like "everything in the DMG is good" and "nothing in the DMG is good."
If I wanted to talk about my overall assessement of the DMG in any kind of meaningful way, I personally would choose to build up my position from a basis of sub-points. But I can't even reach a common understanding of the words "context", "lying", and so on with many folks. If a person cannot even see how I can take exception to this one section of the DMG, then the other places in the DMG where the same things happen aren't going to be explicable either. And a statement like "I don't think the 4E DMG is in the top-half of DMGs ever written" is unsubstantiated.
This in particular struck me as an unfair characterization if your intent is to link the interpretation to the bothersome bit in the OP.
The link was not what was intended by the author, to be sure. But that's actually one of my points.
Seems to me that people's *principles* and *habits* are not always in agreement. It is would not be unfair, IMO, if I were speaking with James Wyatt directly, to bring up this very point: How can you call rolling a d20 to determine success/failure to be a "core mechanic" of the game - when your example regarding a *pivotal moment of an adventure* involves a DM completely trumping the actions of a player through DM fiat (even setting aside the lying part).
What does he really mean by "monkey wrench" anyway? That vagueness could very well consitute all sorts of discomfort on the part of the DM. And given the other parts of the DMG that advocate making sure that most events in the game are of some meaning (don't have players wandering around aimlessly "looking for the adventure"), I think it's reasonable to suspect that the advice given in this section covers a lot of parts of the game.
And thus, I really don't find my statement about the "core mechanic" to be unfair.
You see - if you write a DMG that includes bits of unsubstantiated advice like "don't be unfair to the players" but then your examples and implementations and specifics range from manipulative to down-right dishonest, then I think it's fair for me to take that seriously. Granted, I need to establish those places that I think are dishonest, which I've tried to take a small step in doing.
If folks are generally willing to concede that the passage in question is as I say it is (more or less), then I suspect you'll say "yea, but the rest of the book is great". In which case I can continue with part 2...

(I had no intention of continuing along with part 2 when I started this.)