Okay.. I put this up and got "poster's remorse" and dug a little further.. my research up to this point just consisted of poking around bikeforums.

There's a spiriited discussion on lifehacker.net about this

So it appears that 6 volt batteries are really just a number of smaller batteries in series all cased up. However, they're not always AA and may not be alkaline. So I guess I'll just keep this post up for the benefit of anybody else that comes across this video..