Then I will have to say that you have learned wrong. Storing wet cell batteries directly on a concrete floor is perfectly fine.
The old practice and thinking which really makes no sense since the invention of plastic "WAS" to keep wet cell batteries off of concrete floors. That was when battery cases were made out of "wood".
Since the use of plastic cases for these type batteries have been used there is no long an issue of a battery running down from being placed on a concrete floor.
For about 25 years I stored thousands of car batteries on concrete with no problem at all.