People knew the NRO existed a long time before it was publicly acknowledged, you can't have an office building of that size, parking and sheer number of people commuting to it daily in a regular pattern in a Washington DC suburb without some people starting to talk.

It was kind of a "yeah of course, what do you expect, we don't have this capability?" rhetorical question.

It was known in much the same way Janet flights are known.

Thinking that nasa leadership wouldn't be aware of its existence at all is not accurate, I think, any more than thinking people at certain aerospace contractors didn't know it existed... More like, it was metaphorically over on the other side of a fence that people were not allowed to touch.