[longhornchris04]

Electricity takes the path of least resistance... so splitting the spark doesn't ensure both plugs fire with the same energy, if at all. Additionally, providing multiple paths changes the resistance, which in turn changes the voltage across the gaps.

If the point of twin-plugging is to get better control of combustion propagation in the chamber and prevent secondary ingnition (knocking), then unpredicatable primary ignition seems to be the last thing you would want.

Put another way, if it were that easy then there wouldn't be so many other options for twin plugging.