What we see here is the direct result of governmental censorship that distorted the truth:
The original script was based on the true story in the Lesser Xing-An Ridge, (Xiao Xingyan Mountain in the Plot Summary) in the late 1980's & early 1990's era:
Japanese occupation force drafted huge numbers of Chinese laborers to construct a defensive line of underground bunkers in the Lesser Xing-An Ridge near the end of World War II for defense against Soviet Red Army. Most of the Chinese laborers drafted were dead and buried next to the defense line in mass graves.
Due to the Sino-Soviet ideological split in the 1960's, the two countries were hostile to each other and the strategic location of this place made it off limit to the general pubic as it continued to be a restricted military area. The site was rediscovered thanks to the reform in China and the normalization of the relationships of China and Russia, and the place was planned to be used as memorial site.
However, the rumors of the gold left behind by the Japanese trigger a massive wave of exploration, with the government in the lead, because local officials believed that recovering the treasure would help to improve local economy. Of course, there was none after much efforts spent, but the historical site was totally destroyed in the process.
The original script honestly reflected such stupidity and absurdity and was obviously rejected by the governmental censorship, so it had to be changed to what we see in the movie today.