Deefer Dog, those stats are referring to accidents*. I think most of us with adequate training are comfortable that we would not be part of the accident group and therefore not part of the 50% who shut down the wrong engine.
*Statistics need to be read very carefully in order to make sense of them. The section is poorly worded and I am not sure if they are referring to accidents or PCM+ICR events (engine failure combined with incorrect crew response). Either way, it is not suggesting at all that 50% of pilots would make a similar error.