This is based on essentially gossip, or if you prefer, a rumor. I have been dining in Washington again and someone there who is in fact both well known and very well informed, but whom I shall not name, made a comment about the state of conventional weapons in DPRK and also said that this has not been publicly known. According to this person their condition is much worse than publicly believed. So out of date and out of condition are they that supposedly North Korea can no longer seriously threaten Seoul with a conventional attack (as has long been taken for granted as being possible and looming over the situation there).
The supposed implication of this, if indeed it is true (which it may not be, and this is simply not easily checked on), would be that the DPRK needs its nuclear weapons more than we have thought and will be even less willing to give them up than has been thought, not that many of us have taken too seriously the idea that they would be willing to give them up. Indeed, there have been recent rumblings out of Washington, denied by the administration, that Trump may be willing to return to the position of earlier administrations and cease trying to get DPRK to give up those weapons while trying to put some limits on the program instead. Needless to say, Trump has had nothing but ridicule for this position when it seemed to be that of Obama, but if he does it, well, this will sort of be like calling NAFTA the worst trade deal ever and then negotiation a new NAFTA that is only slightly different from it and proclaiming it to be the best trade deal ever.