Maybe the issue to consider isn't human behavior but rather leadership structure of the group of boys. With the boys in real life on the island who lead and how? There were moments of disagreement and they also had a system of administering justice and resolution. Did they follow the one boy who knew most about survival? That is a very different system of government than a voting democracy. The key is that when one broke his leg the rest provided for him. This goes all the way back to Plato observing city states in Ancient Greece attempts at creating institutions for mutual survival and defense.

Thirty years ago I saw recording of a heated interview with William Golding about the character in the book the boys should have chosen to lead. I can't remember if it was Ralph vs Piggy however I think Golding argued that it was Simon, the Christ like mystic, who would have provided salvation for all the boys if he was followed. Simon represented altruism in the book picking hard to reach berries for the smaller boys who couldn't reach. So in real life when a group of boys who are stranded on island who have religious values, altruism like in the case of caring for the one boy with a broken leg it is like they would have chosen Simon as Golding suggested in his interview to lead.

It might not be a rebuttal to the Lord of the Flies. It is a confirmation of what Golding said about the boys and their values.