Quite literally the first paragraph of the article:
According to Soviet records 381,067 German Wehrmacht POWs died in NKVD camps (356,700 German nationals and 24,367 from other nations).
Or in more detail lower down in the section titled Soviet statistics:
According to Russian historian Grigori F. Krivosheev, Soviet NKVD figures list 2,733,739 German “Wehrmacht” POWs (Военнопленные из войск вермахта) taken with 381,067 having died in captivity.
The issue isn’t just a simple oversight. Git includes the file name as part of the tree and commit hash. The hash has security implications. There’s really no way to make the hash support case insensitivity without opening up a multitude of holes there. So there will always be a mismatch, and you can’t just fix it without changing how git works from the ground up.