They did it to make their test setup look more scientific and controlled. Still, the easiest test would have been to buy 2 devices, open up brand new batteries for each and whack one set in as-is and the other set with Batterisers, and set up a time-lapse camera taking shots every minute until both are dead. Make the photos into a video and post it. Simple and easy proof.
Then repeat with 2 monkeys, 2 radios, 2 flashlights.... very simple actually. Stuff for a middle-school science fair project. No need to understand the "magic" going on in the Batteriser, just measure the device performance over time (speed of movement, light intensity, screen contrast, reception/volume).
Give some Batterisers to a bunch of 6th graders and they will have no problem doing it.