Any proof of this?
They basically give external control to all the baseband processors functions (read mic, control signal, read gps chip etc.)
It's why snowden made: https://www.wired.com/2016/07/snowden-designs-device-warn-ip...
because if your phone is in airplane mode, it shouldn't be transmitting - and they can all be made to.
(Oh, and I have friends who served in Afghanistan, so found out about all this around 2002)