Maybe, but considering the times a successful launch and return of a man I would think would have been major headlines in the Soviet press. The actual launch yea I could see that as secret, but only kept that way if it failed, like the secrecy surrounding the Russians that died during that period. And the video when talking about secrets is mostly training, testing and failure issues. The Soviets didn't want anything to indicate they could make mistakes or have accidents, but wanted to show the world only the "perfection" of the Soviet system and mankind's next step in evolution.