There is a difference between operational secrets and methodological secrets. If you're about to stage an operation against the enemy, do you publish the fact that you're coming? No. But then when the operation is over, there is nothing more to keep secret, and the public can find out what has been done on a timescale that allows them to reasonably cause bad actors to be punished or prevent it from happening over and over.

By contrast, with something like a secret mass surveillance program, there is no "end" where you keep something a secret for 18 months but then everybody finds out about it through official channels, so things like that don't get to be a secret. One way or another the public needs to timely find out what's being done in their name.