Generally, an engine will only stop in one of severl discrete places as once the rpm gets below a couple of hundred the compression will stop it suddenly. Therefore the impact from the starter pinion is only going to be in one of a couple of places so it’s inevitable that some teeth will wear more than others. A broken tooth could be unlucky, or a lazy pre-engagement, or even a dodgy switch / relay that allows the starter pinion to bounce.
Automatic transmissions don’t have a flywheel, there’s plenty enough weight in the torque converter to carry the rotation on past the power and compression spikes in the cycle. They do have a flex plate which permits the converter to float somewhat as well as provide a mount for the ring gear. It’s far more common to see tooth damage on a flex plate than ever it is on a flywheel, but it can happen.
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