Presumably the maps were made from confidential info with the help of Germans in their .mil and .gov... and if like clockwork we had to fight WWIII in the 1970s it would have helped to not blow the cover of those agents. Even more excitingly, in the short term, about 1/4 of those agents probably were allied with the USSR .mil and .gov by 1950, quite handy human intelligence.

Also having been in .mil, troops always have crazy stories that are blown off, but a large cache of rigged board games means POWs would probably never be able to play a board game again, which is a shame, so its vaguely humanitarian, although they must have realized the truth would eventually come out (like now). Its too bad, board games are nice for POWs, and now they can't have them...