Logistic has always been a big problem in military operations. In battlefield, how military tracks its own forces, the deployment and the casualties, in a chaotic battlefield.

The U.S Army had given every soldier a dog tag long before WWII. During WWII, information including First name, given name, social security number/service number, blood type, religion, and last time the soldier had tetanus shot. After WWII, these tags were standardized in all branches of the US military. The US also had well organized file system for soldiers, in a highly industrialized society such as the US which had never had its mainland invaded, all the infrastructure were intact, and most of the soldiers were literate, and the military command chain, rules and regulations and management process had been established. These gave the US armed force a big advantage, yet it took the US many years to track down the number. The final report so far dated 1993.

As for the Chinese, 1949, Oct. 1, Communists officially declared state hood. Within one year, China entered Korean war. Practically, China didn't have much infrastructure dealing with logistic management like the US. Many if not majority soldiers were illiterate, making it difficult to do paper work. That would be no meaningful file system to manage vast among of personnel data. Here you are talking about over million people. Even according Chinese official data, 780,000 troops were sent, that is still a very large number. Chinese soldiers did not have dog tag like metal id, if we assume they had id tag made of cloth, which could have been damaged pretty easily in battlefield, Chinese military had to had hard time to identify death soldiers, The communication bandwidth between the front and the commanding posts was very narrow, and it would not have the capacity to report the list of KIA, MIA and Died of wound.

Chinese also had little modern means of transportation, comparing to the UN counter part, large among of soldiers were infentries. According to the US, Chinese troops typically invaded in small pockets to counter the supeiror firepower of the UN troops, and that made it even harder for them to count losses.

After all, it is not my business to change your mind, you believe whatever you believe. I don't care so much about Korean war. What I care is how to make the US armed forces dominant the future battlefield.