"The specifications start to go overboard for us, though, when it comes to the hardware privacy switches: the device is planned to have no fewer than six which will fully disconnect, at the hardware level, multiple functions: camera, microphone, Bluetooth, GPS, mobile network, and Wi-Fi. That frankly seems like overkill, but we're sure that it will make some extremely privacy-conscious buyers salivate."
Given the number of apps that periodically try & "phone home", want to access GPS, bluetooth etc. then its a good way to keep your internet use down (useful if on a limited data tariff).
Blocking GPS, bluetooth can again be useful - both can be battery hogs, if you are not using an app that needs them then a hardware switch guarantees nothing can use it.
So neither of the above are privacy reasons they are reducing network use & battery use reasons.
Microphone & camera, are obviously mainly for privacy purposes, but can be useful for other reasons (we are all aware of "butt dials" - can be easy to accidentally trigger camera function too - another thing that can be battery expensive & so off at hardware level is a benefit again)