I don’t get why they’re suggesting that iPhone communicate to each other to reboot. I mean, what do the iPhone gain? Both have the system time and know for how long they have had no mobile network. They don’t have to set up complicated communication for that. What does the other device know more than the iPhone that makes it know that it has to restart?
Why could it not be something like Find My iPhone lock/reboot request is an encrypted packet that is destined to arrive at iPhone with Serial Number XYZ. Another iPhone gets near the target iPhone and shares its presence with Apple. Apple has been waiting to deliver this encrypted signed packet from Find My iPhone network to the target device. This packet is sent to the iPhone in range and then the data is delivered over AWDL.