I really didn't get that vibe from DMG1 at all
Agreed (and XPed your post before I noticed you'd said this other thing that I agree with).
some of the research done before 4e came out that sadi basically people wanted to be free of built in fluff so they could make their own and not feel restricted by it.
Perhaps 4e went to far in that regard but I can see it as a rock and a hard place as a designer.
I don't think this characterization is quite accurate. Certainly, the mechanics received a great deal more attention than the fluff in 4e. That much is true.
I tend to disagree with these statements. Of all core D&D rulebooks, 4e seems to me to have far-and-away the most setting/flavour built in. There are a couple of pages of gods, political history built into the race descriptions, mythic history in the DMG and in many of the MM descriptions, etc.
There's a gameworld there. In comparison, the 3E PHB is far more spartan (some gods, who receive less detailed coverage). And Basic was more spartan again. The only thing I think that compares is appendix IV of Gygax's PHB - there's a lot packed into that one page!
(Some might want to put forward the maps and gazzeteer in the old Rules Cyclopedia. I personally don't think there's as much there to kickstart a game as there is in 4e.)
In 4e, the fluff of a power is almost immaterial. With shockingly few exceptions there is no mechanical difference between an arcane power and a martial power that has the same effect.
<snip>
What it costs is the ability to reason about a world mechanically.
I think your comparison of arcane to martial powers might be underestimating the signficance of keywords. Nearly every arcane power has a damage and/or effect keyword. Nearly every martial power lacks such a keyword. This is a mechanical difference that has a big story impact. For example, it's very important for page 42 - how do we know that Fireball can burn a building down but Come and Get It can't? Because Fireball has the fire keyword and deals fire damage, whereas Come and Get It doesn't.
But I agree with you that reasoning about the fictinal world mechanically is more limited in 4e than in earlier versions of D&D.
I think the game has two subsitutes for that sort of reasoning (and in this, it resembles other more abstract systems like HeroQuest). First, there are the genre constraints implied by the various fictional elements presented in the rulebooks. (And this is where flavour text can matter, because it suggests a genre, even if it is often disregarded in action resolution.) Second, there are the guidelines to GMs in repsect of DCs, damage etc which provide a reassurance to all the game participants that nothing is going to go horribly wrong as long as situations are framed within the indicated mathematical parameters. (This is part of why "the maths" is more important to 4e, I think, than to other versions of D&D. Because if the maths is wrong, then it can't provide this needed assurance function.)