The pinion isnt really spinning but the shaft is so there is an inertial shock when they engage, I think that most of the flywheel wear occurs when the engine starts and the pinion throws out, the inertia working once again but this time the engine starting spins the pinion faster than the shaft can accelerate so it throws out instead of in.
The bendix mechanism of an inertia starter motor was a really clever invention in its time.
Great description of the "Wow--err--err-- Wow--err--err -- Wow"
The people around where I live here in France are somewhat simple, they cannot string a sentence together without lots of "euuhhs" never more than 3 seconds of speech without one, often just a few incoherent words strung together with "euuhhs" so you have to try and guess what they are trying to say. When a group meet together for the mandatory shaking of hands, kissy-kissy and chit chat before a club session or whatever it always reminds me of a convention of lucas inertia starter motors