This demo is all local mesh, the phones are communicating directly via Bluetooth.
To talk to someone in another country will still require internet.
Discussion
So what's the point? AFAIK BT is a 10 to 30 yard range?
Bluetooth 5 LE can reach further than that, some sources claim 435 yards in long range mode and free-space environment.
I didn't know that but still, hardly practical.
I personally can see it as a communication channel if you go to a large event (eg. peaceful protest), but want your phone in flight mode for a reason.
Or a concert event when you are trying to find your friend while celluar being overloaded or not present...
The point is that these phones create a mesh network. The network being formed by the connected devices, and extensible in both range and size by new devices joining, and doesn't depend on external infrastructure like telephone lines or internet. It's like a BT LAN.