Trying really hard not to be snarky here, so please take the following as honestly curiosity of me not understand some of the points you are making.
You just agreed with blizzardb that the DMG indeed says what he quoted. Which totally goes against one of the problems you have with 4e. Does this mean that if you haven't read whatever module you are referring to, and instead just the core books, you wouldn't have this problem with 4e? Or does this mean that because some of the modules have problems, the system is flawed?
No snarkiness detected. Well done

In point of fact, I have not read any modules. This is a perception I have picked up almost totally without basis. I believe the system encourages modules to be written in a certain way. It is my opinion that that certain way is to encourage the use of level appropriate challenges at all times. (be it combat or locks)
The extrapolated example might be one where the bedroom doors at the inn are made of adamantine because the characters are participating in a level 30 adventure.
As with any extrapolation, it is subject to great skepticism, but it does well when understood as being a pure example of what is possible.
I haven't ever run published adventures, so it is somewhat of a moot point with me personally. However, I am an unwilling convert participating in a 4E game, in a published adventure (KotS). My experience thus far (with 4E and with published adventures) has not in any way improved my disposition towards the new system.
While I would be hard pressed to present examples from KotS (due to not having owned/read the adventure) I have certainly felt like every potentially challenging event has fallen within the level appropriate range, regardless of whether that makes for a good story or not.
To answer your question more directly. Flaws in the system exacerbate the problems that I have with published adventures in general. In this particular example, the flaw is one of emphasis, not of hard and fast rules or of wrong design intent. My preferred style of play dictates that level appropriate challenges should not be as frequent as the DMG indicates.
My not being already aware of the point raised by blizzardb is caused by a separate flaw of the system. Namely, that I find the books unpleasant to read, and therefore haven't read them as much as I should.
I read the 2E and 3.0E books extensively when I got them, but found I was unable to do so with 4E. This seems to be a common problem judging by the number of people who, as you put it, "do not realize that some of their problems with 4e derive from a lack of understanding of the rules, instead of something else."
My dislike for the rules, and my lack of understanding the rules are two separate issues. Neither is
caused by the other, but one may indeed be contributing to the other. The two are separate problems, but together they present a problem which is greater than the sum of its parts.