That's what I'm thinking. There's too much info there. I'm also unsure of that guy being affiliated with the government. Just doesn't sound likely he would be sharing that much info on public message boards that should probably be classified. I dunno though. This all get more complicated as time goes on. (Proper typing for easier reading ;)
Yes that does seem suspicious ... certainly anyone in the US military or intelligence community who blabbed that much about things that would appear likely to be classified would be subject to court-martial or worse. Though stranger things have happened.
Let's look at the nuclear angle for a moment. Real nukes are a big problem for a group that doesn't quite amount to a nation-state ... since as far as we know al Qaeda has not tested any nukes (and this isn't easy to hide from the seismologists), they have no way to know if any home-grown nukes would work. Things such as suitcase nukes would require lots of maintenance since they have a short shelf life ... and if they have to do too much maintenance then they'd want some assurance that it was still operational. Add in the problem that an unsuccessful attempt would have the potential for severe "blowback" without causing us much damage at all. The result is that a traditional nuke may well be too risky from their point of view if they couldn't be certain that it would actually work.
So the obvious thing is a dirty bomb ... a very low tech device, all you need is some assorted hospital or industrial radioactive pellets, an ability to mill them, and almost any conventional explosive charge. You'd get almost as much bang for the buck, so to speak, since people are irrationally afraid of anything radioactive - it might be hard to convince people it was really safe to return even after everything was cleaned up. Plus you can play the nuclear angle back home with the ignorant masses in the mideast most of whom are equally misinformed - most non-technical people in the world hear the words "radioactive" or "nuclear" and think "bomb." So they could make it sound like a whole city was really "destroyed." What could be better? You get all the benefits and none of the risk - except the risk of blowback of course, but they'd be counting on the US being so terrorized that we'd be afraid to do anything.