I had heard the same thing many moons ago from a Deka battery rep...I'm not sure what the batteries cased were made of back in the 50s and 60s but the "myth" came from the idea that the concrete will "pull" the water/acid out of the battery. With today's plastics it's not a problem.
Bakelite may have been the old material and it may have been porous.
Again--True or not??