This 'tactic' was classified until leaked, so I don't think its purpose is to scare the public. My guess is that they just want tons of ciphertext samples to use in future cryptanalysis work.
Since he's apparently now deep in debriefment with the Ruskies, this would have been a brilliant counter-intel maneuver, leveraging the prejudices of all of us chattering morons to fake out everybody in the world.
That it would have been brilliant, is how I know that General Surveillance and his minions didn't do it.
There's absolutely no evidence that's true. People are just speculating that the Russians might want to do that. As far as anyone knows, Snowden is still sitting in the transit area of the Moscow airport and has never left that location so far.
This 'tactic' was classified until leaked, so I don't think its purpose is to scare the public. My guess is that they just want tons of ciphertext samples to use in future cryptanalysis work.