I think people have the wrong idea when the revolutionary leadership of the Korean Workers' Party decided to "recognize" the Republic of Korea in the South.
The real meaning behind this decision is the removal of the barrier to normalization and unification with the South, something that has been talked about since the 90s. Now the Democratic Republic is strong enough to assert itself. He saw through the mock talks between the South and Trump, who lied about lifting sanctions during his first term in office. That is why he said according to its constitution that the border between it and the south is not defined.
This means that nuclear can be used in the South, the South is seen as the most hostile country, and fundamentally different from the North. It is less Korean than a Western culture of what is supposedly Korean. In this context DPRK is the only real Korea out there and to bring Korea to justice it must be annexation, integration and assimilation, similar to the Russian model in Ukraine.