Conversely, a Linux system with no verified boot can be easily tampered with without the user detecting it by people lower than the government such as casual hackers. So in a world where your government is going crazy, you're opting for an operating system that can be penetrated with relative ease (e.g. with persistent root malware) both by a non-government hacker on top of a state backed one.
I'd also guess it's much harder to securely source components for a Linux build in the way Apple is able to.