tl;dr: Stories focusing on the positive aspects: Good. --> i.e. George Washington and the Cherry Tree Stories focusing on the negative consequences: BAD. ( Pinocchio , The Boy Who Cried Wolf )
The George Washington story matches the subsequent experience of the child. The child is asked if they did the bad thing, just exactly as George Washington was asked in the story. A very young child will be able to make the connection between what is happening and the story they just heard because the exact same thing is going down.
The other stories are more abstract. They are not stories of someone doing a bad thing and then being asked if they did the bad thing.
It's a more reasonable conclusion, in my opinion, that what we are seeing is an effect of how close the story is to the experience, without having to rely on abstraction skills a very young child does not possess. And not whether the outcome was good or bad.
In general the study design is poor and more people should have seen that. There are numerous differences between these stories, hundreds of differences, not just outcome. And one of the stories being much closer to what they are testing is obviously relevant and confounding.
A better study design would be able to explore this. For example, tell the children one of the following stories:
1. George Washington does a bad thing and is asked if he did it. When he says yes, he is rewarded.
2. George Washington does a bad thing and is asked if he did it. When he says yes, he is punished.
3. George Washington does a bad thing. He is not asked if he did it, but is rewarded by fate.
4. George Washington does a bad thing. He is not asked if he did it, but is punished by fate.
5. George Washington does a good thing and is asked if he did it. When he says yes, he is rewarded.
6. George Washington does a good thing and is asked if he did it. When he says yes, he is punished.
7. George Washington does a good thing. He is not asked if he did it, but is rewarded by fate.
8. George Washington does a good thing. He is not asked if he did it, but is punished by fate.