North Korea has mobile launchers. It could have miniaturization know-how too.
You do not know the level of North Korean miniaturization technology. You cannot claim North Korea cannot deliver its atomic weapons by ballistic missile.
Firstly, North Korea had surprised western experts with its first atomic explosion.
Secondly, North Korea can always get help in their nuclear program. Notice the mobile launcher. That also surprised western experts.
Hence, it is unknown whether North Korea has miniaturized atomic warheads. Are you willing to bet South Korea's existence on the unproven theory that North Korea cannot launch atomic warheads on a ballistic missile?
** FILE ** In this April 15, 2012, file photo, a North Korean vehicle carrying a missile passes by during a mass military parade in Pyongyang’s Kim Il Sung Square to celebrate the centenary of the birth of the late North Korean founder Kim Il Sung. The enormous, 16-wheel truck used to carry the missile, likely came from China in a possible violation of U.N. sanctions meant to rein in Pyongyang’s missile program, experts say. (AP Photo/David Guttenfelder, File)
A missile is transported on a vehicle during a military pararade April 15 commemorating the 100th birth anniversary of former North Korean President Kim Il Sung in Pyongyang. (KCNA via KNS via AFP)