Any question over the legitimacy of these documents has long since been resolved. The information is out there, and at least some of it (the official documents at least if not Snowden's commentary) is confirmed to be accurate. You can't put that cat back in the bag, so the military is not revealing anything by blocking those sites - especially since the block is broad and doesn't shed any light on whether specific portions of what was said is accurate.
The other (and arguably more important) purpose for continuing to treat classified information as classified until it is officially declassified is to prevent disclosure of even more secrets. Without doing a carefull study of exactly what has been released, what has become widely spread and confirmed or not, and how it impacts the mission at a high level, you are highly likely to inadvertantly reveal (or confirm, or draw associations between) other sensitive information.
There are lots of ways this can become complicated really fast. Someone working on some portion of a project may not realize why some information about another part is sensitive since it is harmless information for their part of the project. The leak itself may result in a change in what is classified. For example if X and Y are completely non-sensitive on their own but combined allow you to infer Z which is classified, it is customary to pick one of them to treat as classifed to protect Z, while the other remains FOUO. If X was being treated as classified and is now leaked, but Y and Z are still secret, then it may be prudent to start treating Y as classified going forward. It is also possible that even though a specific detail has been leaked, the enemy didn't understand it's significance or what it meant at all due to lack of context, so it does make sense to continue treating it as classified, even though it is already in the "public".
So until someone has carefully considered all these factors, developed a new classification guide, trained everyone on the new guide, and resolved any ambiguities that come up while implementing the new guidelines, it really does make sense to continue treating the leaked information as classified. Even if "common sense" might make you think it is a pointless exercise.
PS: This is a justification of the rules regarding legitimately classified information. I am not justifying the fact that these surveilence programs existed, or that their existance was classified in violation of the 4th ammendment.