By way of example, Rod was able to facilitate hardware level duplication (and could have easily performed neutralization though he did not) of the Permissive Action Link nuclear keys in the active german theatre which were also in locked safes on one of the largest US bases in the world behind many, many layers of armed soldiers.
Correction: we didn't do that in the unclassified literature. PERSEREC did a deep dive and that deep dive remains behind the Green Door (same with Hanssen's, Boyce's, and Ames's, among others).
Imagine if they were given up by a human source. That kind of thing doesn't leak until everyone is dead and buried, and even then it doesn't always get out because it gives foreign counterintelligence services some ability to assess the damage done by the source.
Imagine if they were given up by a technical collection program. Same thing.