Just a theory ....
If people with something to hide believe a channel is being watched, they're likely to avoid it. Even blacklist it, so dumber members don't stumble in.
So feed information that $channel is being monitored by $spook (of whatever country in the alliance), and that's one fewer place they're likely to use.
So, make announcements like this, and delegate someone to sample the channel in question a couple of times a year (and a dumb bot to run full-time). Repeat as necessary until they're channeled into somewhere you really do watch. Gotcha, for relatively little actual expenditure of effort.
No of course I don't know it's any such thing. But who's to say it's not?