There's a part in there where he says "you never see a remote(etc) with batteries (in the same orientation)", but I have had numerous such devices where both batteries go in the same way, and they just use traces on the PCB or wires to deal with seriesing them, simply to make it much easier for the user to put htem in, I guess. (although many people still put them in backwards, as I have "fixed" lots of "broken" devices just by reversing the batteries they put in).