I hate to say it but you get what you pay for - their brand distilled may be the first runs through systems producing other brand lines or lacking some final filtration. If it is purity you want pay the going rate for bottled water from the local drug store, etc.
I have another question - What about Ozone? Many bottled water products are finished with ozonation as final insurance keeping the product sterile until it is opened. I believe the bubbles seen clinging to the insides of a fresh gallon jug consist mostly of ozone. Is it harmless over long periods on lead plates of flooded batteries?
