They are erroring on the side of caution because people have determined secret information from public information - like the energy in a nuclear bomb (censored) by the blast radius (public).
Another example is they want to protect their means and methods. But those means and methods are how they know most information. Often times it's easy to work backwards from they know x therefore y is compromised.
It's a hard problem similar to how to release anonymized data. See K-anonymity attacks and caveats.
