I assume that the chain going out at speed is always going to do major damage. On the otherhand have lost timing belts on interference diesel engines either at startup cranking or when the engine was just turned off. On both occasions there was no colateral damage. Think at very low revolutions perhaps the hydralic lifters compensated enough to prevent the normal damage. Just a guess though but the engines rolled totally over many times before I knew a problem existed and went looking. Assume the newer mercedes engines with hydralic lifters might fare the same way other than the chain is more likely to part company at speed.