You could kill cameras individually and separately from the microphone: Would then need three switches instead of one.
You might want to kill Bluetooth separately from WiFi; two switches instead of one.
You could have a separate switch for accelerometers. And so on, there are many small things you just might want to turn off.
The set of three is probably a good compromise, if you want those switches on the outside of the phone. (The Pinephone has them internally, IIRC.)
We had some entertaining discussions about kill switches - and design suggestions - back when there were no official designs. I especially remember this comment 