Interesting that it's a mechanical design and not an electronic solution, which was my first intuition.
One interesting thought: is the lack of battery installation diagram going to cause consternation in consumers who are by now very accustomed to battery installation diagrams?
That was the first thing which came to my mind as well. I thought they've probably got a bridge of schottky diodes for every battery. The mechanical design makes it seem very elegant.If it were a schottky bridge, it'll still have a forward drop of ~0.3 - 0.45 volts, which is pretty big for 1.5 volts batteries.
One interesting thought: is the lack of battery installation diagram going to cause consternation in consumers who are by now very accustomed to battery installation diagrams?