Then I'm not sure why this is a story. We've been flying planes over South Korea for more than 50 years.
I suppose if they flew a nuclear-capable bomber along the southern edge of the DMZ -- perhaps supersonic and with afterburners going to make a big noise -- then perhaps it might be seen as a message, as opposed normal flight ops.
No idea if that's what actually happened, but it wouldn't surprise me if it did.
