Interesting; but on the Stihl TS500i, it is crank triggered by the crankshafts counterweights with a sensor through a hole in the bottom of the crankcase.
It does have a flywheel keyway, but it's just to aid in tightening. The same sensor reads atmospheric and crankcase pressures inside the crankcase, temperature, crank position, and mixture.
Amazing, and I've never seen one fail yet out of probably close to 300 I've serviced.
*
On another subject, I saw a public request for an "in suit" crapper design on the Weather Channel this morning. Maybe NASA should get the team who designed that sensor to figure out how to create an "in suit" crapper for extended-stay space travel.
Or maybe ask the guys at area 51 to ask the aliens how they did it, lol.....