> ...the end of the article seems to be acknowledging that families have phenotypes; there's no reason this shouldn't apply to groups.

You state that "there's no reason this shouldn't apply to groups", but that's the critical question under investigation! Namely, do the behaviours (that you're classifying as a part of the phenotype) provide evidence for group selection, or are they adequately explained by kin/individual selection? It's a given that group selection could occur, but where is the evidence that it does occur?