I think the test is happening, graphene activation, probably not. It might just be a real test of the system to make sure it works. But what’s next when they‘re sure it works and they know they can hit all these devices at the same time. 
Kinda creepy tbh 

 Here’s the official press release

https://www.fema.gov/press-release/20230803/fema-and-fcc-plan-nationwide-emergency-alert-test-oct-4-2023