The reality is that conspiracy theorists aren't interested in learning how things actually work, which is why they're conspiracy theorists.
In reality your phone is a significantly bigger threat to privacy both in terms of normal day to day monitoring (e.g. location tracking) and even listening in (a closed source baseband that can communicate on a platform you cannot even monitor).
When people see the GPS is on all the time or can look up their location data off their phone, it feels uncomfortable, but then they make un-encrypted phone calls through ma bell and let their location get sold.
People are really bad a privacy and key on these obvious, invasive feeling, technologies but then miss the bigger picture.
Conspiracy theorists have less faith in authority figures, which is why they're conspiracy theorists.
Whilst offline, is it possible for the device to store audio?
Is all writable storage auditable by users?