Look at it this way:
Even in 1947 they knew what "Top Secret" meant. And the thought that a general would stop off at the safe, balloon under one arm, for a top secret memo to wave around in front of the people to whom he's lying -- that is pure horse manure.
I've no doubt that there is more to this story -- some deep secret that they're still lying to protect.
But that doesn't prevent this story from still being crap.