The idea that iPhones magically communicate with each other to “reboot randomly” when off a cellular network (assumably would happen on a plane easily) is pretty far fetched. The far more likely explanation is that iOS 18.0 has some radio/modem bugs that causes devices to randomly reboot, likely correlated with long periods of disuse or lack of network connectivity.

Or heck, if the phone thinks the cellular modem isn’t working (like the phone in a faraday cage), some watchdog might just timeout and reboot.

In any case, the idea that they’re randomly networking and intentionally rebooting to thwart this specific law enforcement attack seems pretty unlikely.