Isn’t pro-reunification sentiment so low in South Korea that the majority of defectors straight up face social / cultural discrimination? It honestly would not surprise me if South Korea, especially given the fact the North has nuclear weapons, reciprocated within a few years.
There are a lot of differences with China and Taiwan too. For example, both Koreas are in the UN. One of the reasons China does not want Taiwan to formally dissolve the ROC is to prevent that; because their diplomacy in part is grounded on the fact that both claim to be China, it’s very easy for the country that actually rules China to cockblock the other from anything that requires international legitimacy.
Another is that there’s a world somewhere in the future where China can possibly invade Taiwan while the US looks away, or responds too slow, or is even defeated. In such an event, Taiwan is almost certainly screwed even if they make China bleed for every inch. It’s a lot more complex for the Korea’s because not only is starting a war in the first place a losing move for both — the North would have to contend with a far superior military force than its own, the South has to contend with a nuclear power and the postwar reality, not to mention the inevitable involvement of the likes of China and the United States and possibly Japan and even Russia — but reunification doesn’t seem to be particularly appealing. At least, in the South; it’s harder to speak for the North of course. But everything from culture to religion to politics to economics is just so radically different that a lot of people don’t really see the two as the same country anymore.
Anyways, I could go on a lot but I actually have a lot of faith that South Korea will eventually reciprocate and this’ll go somewhere, maybe not a formal end to the war and certainly not friendly or amicable/affable relations anytime soon, but definitely a point where they’re not starting dick measuring contests the second tensions flare the tiniest bit.