You know, that is exactly what I was thinking.
Then I read the last two paragraphs.
This isn't about what is or isn't possible in such a scenario. This is about letting NK know what we're prepared for. Letting him think they might have a day or so to 'sue for peace' while shelling Seoul is stroking Kim (whatever the potbelly little fool's other names are) 's ego. Even while letting him know that we know. Since the red phone is down, there's really few alternatives left. Email isn't secure, but public information is hard to tamper with, since it can be multiple sourced.
And you can be sure this can't be hidden by his people. He's an internet hound. He'll see it.
And when he does, he may just have a 'moment of clarity'.