I agree with Christelyn that it's probably more a situation of «In social settings people of similar phenotypes often gravitate toward each other when other «unknowns» are present.» (beyondblackwhite.com)
A considerable genetic heterogeneity is expected within and among studies, as different combinations of the various alleles of the multiple genes and epistatic gene interactions may produce similar phenotypes. (capmh.biomedcentral.com)
Although uncommon, identical changes at the DNA level between humans and dogs with similar phenotypes have been previously identified [35], [36]. (journals.plos.org)