True socialist interpretation of the "Mauer": It's to keep the fascists out, not to keep the own people in. Really!
I think it's just more of a way to throw in a cheap reference to real history regardless of how much it fits the context. I.E. Commandante Teste would drop the Maginot Line or a Chinese ship would drop the Great Wall of China, regardless of its actual use. (Or for that matter, how Brits only eat Marmite and stargazie pie while Americans only eat fried butter and Italians are all gelato and pizza.)
