They said the lack of evidence of social stratification in the burial sites and house sizes contrasted with other sites near by. Plus remember this is the headline a news site chose not the scientists.

It's very plausible journalists (including university PR teams) care more about social elitism than the archaeologists which is why it's the HN headline. The archaeologist is just using the only evidence they have which is some pipes, a cemetery, and few remaining structures to extrapolate about the community.