With some further investigation I found this article and some basis for the Old Guy Theory 
http://www.thebatteryterminal.com/TechTalk_Batteries_on_Concrete.htm
Still puzzled by the surface “grime” thing though, it almost contradicts everything he said previously?
…I really enjoyed the “Grandfather Clause”
Ponder this!
A storage battery on a trickle charger is a completed circuit.
