I can't speak to the engineers thought process, but here's what they effectively built.... 2 single cylinder engines on a common crank.
Consider... each cylinder has it's own carb, it's own point and condenser set... it's own coil.
Fry a coil? no problem, it'll still get you home on one cylinder. Carb goes bonkers? Shut that petcock off and ride it home. She don't like runnin' on one cylinder... but she will.
I once had a set of points go out/fry on me up in the mountains of Idaho. Nearest town was about 20 miles away... home was 30. It got me home on one cylinder. That's gotta be worth sumpin.