I think this implies that any attempts to talk about amnesty for Snowden on the condition that he reveals what he took is not a genuine conversation.
On the other hand, if you view Snowden as an adversary, you wouldn't believe him when he says, "I intentionally left clues." When you look through what he could have taken, see the alien landings or whatever, and you don't see his "breadcrumbs" on those files, you probably still shit your pants, because it is actually possible he is lying, and does have a copy of those Roswell documents (or whatever it is, I don't think it's literally aliens).
But if you don't believe him, then why would you trust him to give you everything he took?
To me it seems a dangerous game to give US intelligence any more information about what you know. At every turn they're going to use what they know Snowden knows. For example, if they really did have absolute knowledge of what Snowden took, they'd be able to craft a story that took the leaked information into account but protected all the shady stuff they're doing that Snowden didn't take.
Given that our government doesn't even consider punishing US intelligence leaders when they outright lie to Congress, maybe they don't need to worry about getting the story straight.