Ah the old chestnut about why are there two ignition systems and pugs per cylinder. The books say increased efficiency and redundancy.
The real reason is that Americans dint know how to;
a) design a cylinder head that actually propagates a resonable flame front
b) they cant design/manufacture a reliable ignition system, so they have to have two.
christ they cant even make engine parts that conform to their own drawings.
Messors Porsche, BMW, Mercedes, Ferrari, Lamborgini, Audi, Volkswagon etc etc have never had to fall back on flimsy engineering practices like Lycomming and Continental. Have you ever driven an American car lately??
So the text books are more of a marketing coverup, smoothing over a lack of engineering talent.