One thing to keep in mind is that the author’s interest lies in the nature of nuclear secrecy, and not necessarily the secrets themselves. It’s a subtle distinction but I think explains why the author finds the fact that this type of diagram was officially released by a national lab interesting, even if the information has previously made its way to the public domain in other unofficial ways.

speculation can be found on Wikipedia, perhaps accurate speculation, perhaps not.

DoE contractors leaking details that confirm that speculation would indeed be a big deal, and might well save adversaries some real time and mistakes they’d otherwise make.