TLDR it's so that we can seamlessly synchronize settings and events between them. When to charge from solar, cheap utility rates, or when a storm is incoming.

Consumers (incl me) will not update their 2nd Pila to their new Wifi password when they change it, or not even pare it properly with their first to start with. Also, in an offline situation like a power outage where the internet goes down, you won't be able to communicate over the cloud and synchronize them there. If our servers ever go down (they won't) then you want to be able to rely on local communication.

The local mesh is going to set up new follower devices over an open MQTT api and talk to each other over it - but yes it's more of an enable than a feature in and of itself.