I think the idea of it being an actual "bunker" came from use here, but it was meant to be a basement in someone's house that was used from day to day but was also a place where one would be safer during a storm or some other dangerous situation because there aren't any windows that could be broken or from where the "bad guys" could see lights on, inside. That setting created a sense of urgency and danger and the idea is that there would be a time when refuge from the world would be needed because they'd be on the hunt for JW's.
The whole video was filled with subliminal suggestions that were intended to play on ones subconscious. You're not supposed to think too much about any of it, you're supposed to feel the message. The things we believe to be so, that are held in place by an emotion such as fear, are very difficult to get rid of, even when we know on a conscious level, they are not real. The folks at the Watchtower know this to be true and see this a spiritual warfare and for our own good, rather than deceptive manipulation.