I am not sure which devices you are talking about here, but if you are referring to the Librem14 or the Librem5 phone then I can inform you that in these we actually do sever the power to the respective device using the kill switches and not just flip the #disable line as most other do. When flipping the kill switches in our L14 and L5 you will notice that these devices (like WiFi, Bluetooth, cellular modem etc.) actually disappear from the system (PCIe, USB, SDIO). They are off and no software can re-enable them (except that software control a robot finger that flips the kill switch again 
Cheers
nicole