As it appears the book points out. One of the reasons the war in Korea last as long as it did. Is the Communists wanted all their POWs released back to them. The UN said those EPWs should be able to choose.
As the war dragged on with little movement of lines, e.g. along the 38th Parallel, etc. Once the UN decided it was not going to try to push North and capture Pyong Yang, etc.
And the Koreas would not be united under free democratic leadership. The South's leadership just opened the gates of their EPWs' camps holding the Chinese and some North Koreans. Some wanted to go back home and were repatriated in the agreed upon manner. It seems especially many of the North Koreans. They even rioted in some and had to be put down with extreme prejudice. Most it appears were so thoroughly indoctrinated want to go back to their North Korean version of a Communist Workers' Paradise.
But as we see many Chinese did not want to go back to the Communist Workers' Paradise of China. And after released just blended in the population, go to Taiwan, etc.
And as we see the DMZ roughly along the 38th Parallel remains today. As I have said before I had 2 tours on the DMZ, '84-'85 with a US M113 Mech Bn. Even then we expected war could breakout at anytime. And prepped as if it would.
But this time we[the ROKs & US + hopefully other UN forces(?)] would push onto Pyong Yang and beyond. Unite the Koreas under the democratic South. Break the stalemate/Truce that has been in place since the summer of '53. And destroy the criminal North Korean regime.
As opposes to in Europe our mission was only reinstate the IGB. For obvious reasons …