Which one? There were four.

(That was rhetorical, by the way, my point being that ignoring three presented sources to nitpick one does not a solid argument make)

"This is not at all the same as creating a policy and not explain to the citizen you represent why you are doing it."

Sure, but that wasn't what I took to be your question/request, nor does it really make any difference here when evaluating whether or not the United States has a century-long tradition of wanting to keep military/security information confidential.

The "logic" here is that the mere act of telling the general public why said policy was created would reveal sensitive information about ongoing security activities (information which - allegedly - is indeed of use to the enemy). I disagree with that logic and its application in this case, but that is the logic, and said logic is - as demonstrated previously - precedented in American military history.