I haven’t read full document but I’m Polish and remember that back in the day when buying some games off Steam you’ve got some kind of eastern European version that was separate from global one.

Other than DLC being incompatible, the biggest pain in the ass was that the language selection was very limited, commonly just Polish, Lithuanian and Russian (which nobody speaks here). If you weren’t fan of localization or wanted to play game in the English or original language you were out of luck.