I've definitely noticed this while playing in StrangerVille. Almost all townie households spawned for StrangerVille are single-Sim adult households, with the occasional single-Sim elder household peppered in. Very rarely do I see any young adults.
Strangerville generates a lot of single Sim households, because it has roles unique to just that world: like the infected Sims, military, conspiracy theorists, and scientists that are all needed to complete the story. I will say it starts to seem excessive after awhile, but it's been that way since the pack was released.
