And even up until 1972 the command economy in the north and the (more) liberalized economy in the south hadn't really diverged. NK's growth slowed as they lost

And even up until 1972 the command economy in the north and the (more) liberalized economy in the south hadn't really diverged. NK's growth slowed as they lost the support of the USSR and went negative during the collapse. Not really what you'd expect if authoritarianism was the cause of economic collapse, but exactly what you'd expect if during that time, a hostile state ascended from superiority to supremacy. It's absurd to view the Koreas in isolation since they were both extremely obviously the subjects of a proxy war in which one side lost decisively. The two countries' economies were driven by export and the US and USSR were by far their largest partners. That wasn't an accident.