The batteries although manufactured by the same company sometime even on the same production line may not be the same. The customer dictates the specs and cost, in the case of Wal Mart they are big enough to ask that certain parameters be met while a smaller customer may have to use relabeled Wal Mart spec batteries.
I worked in a factory making Television CRT tubes. While my paycheck and the building both said Sylvania on them,we made CRT,s for every television manufacturer. Most were identical no matter the label the finishing department put on them. When dealing with an established technology the is no profit in constantly reinventing the wheel, you just add or subtract minor features mostly for marketing purposes.