2nd point first: Even if a piece of data is in the public, there is no guarantee of provenance for the data without an official statement. How do you know wiki

2nd point first: Even if a piece of data is in the public, there is no guarantee of provenance for the data without an official statement. How do you know wikileaks or someone else hasn't inserted specific, falsified records into the document trove? It may or may not be classified or secret data. Anybody can slap 'secret' on a document. By not saying anything (neither confirm nor deny), folks with a clearance have to assume it's classified, and they have signed many NDAs and other bits of paper agreeing to not seek access to classified data without the 'need to know'.