I think there might me a simple explanation for this.
Nonreligious children tend to be richer and come from richer countries. Having more wealth means they do not attach as much value to material goods, so they are more "altruistic". Likewise, wealth shields them from the consequences of negative actions, so they are less "punitive".
Nonreligious children tend to be richer and come from richer countries. Having more wealth means they do not attach as much value to material goods, so they are more "altruistic". Likewise, wealth shields them from the consequences of negative actions, so they are less "punitive".