Id think this being the 'official' political position , it would be referring to the end of hostilities when the armistice was signed.Legally there was no ceasefire/capitulation etc and i would suggest as far as the North are concerned barring outside interference they would have prevailed. Hence the stressing of the position that they are one entity 'politically' - certainly not that 'physically' they are one untit , also why they would hold/reunification talks from time to time and family relatives exchanges between the two.

They are cognizant that there is a DMZ , and that theere exists a polity on the south that keeps sending usb filled baloons , propaganda loudspeakes blaring on the Border. So mostly a poltical position being staked out , which is also why the maps only have Palestine and Western Sahara.Not because they are unaware of the situation insitu but geopilitically they are staking their claims.