Snowden did have a difficult time in HS and he does not possess a formal CS/technical education. He was a sys admin, not an engineer. His claims, in that light, do seem bizarre and uninformed. I mean, ffs he seemed to insinuate in the Guardian interview that the NSA keeps a list of undercover assets and he had access to it!? These are the people who created selinux -- if I extend him some credibility, I doubt greatly that he had any real idea what it is he was looking at.
Elsewhere he talks about every machine being bugged and things like that. And the tapping he claims to have intimate knowledge of -- that kind of stuff would be happening inside of some kind of data store, maybe like Apache Accumulo which the NSA also developed. Let alone the implications of what he's saying on the security of all crypto systems everywhere -- how many uneducated sys admins do you know who can inspect a data store and actually understand what they're looking at, and also understand deeply how consumer encryption works.
And this all presumes that the NSA's systems are so poorly configured that a contractor in HI could access all this. My verdict is that all he had was some slideshow that he turned over to the Guardian, the rest is a bullshit story.