I worked for an early stage dating app. We didn't have a full-on playbook per se, but the plan was/is to rollout on a city-by-city basis. For social networks it makes sense to build communities locally before expanding (better to have a community of 1000 in one city than 100 cities with 10 each).
I believe it simply comes down to making the best use of resources and money. If we directed our limited budget to one city the idea was to perfect our acquisition strategy and then apply the learnings as we expanded. It also makes sense to rollout geographically to areas that fit your target market (e.g. dog loving cities)
Hope the perspective helps.