[maxter]

That was my first reaction. Why are they admitting to this? What is their advantage in doing so?

[Eric in the Ozarks]

Since the mid 1950's, any time NK wanted something from the west, they discover and repatriate the remains of Americans killed in action from the Korean War. There was evidence they had a stash of bones to "sell" for food, oil, etc. The recent "admission" of kidnappings, nuclear development, etc., must mean they are out of bones to sell.

[LisaFab]

Why are they admitting to this?

Because they see the writing on the wall. Since they now realize that the "Axis of Evil" designation has teeth and was not merely rhetoric, they have been making concessions for months to show they do not want to be next on the 'list'.