Does disabling Siri disable this behaviour though? What if you're not close enough to the device at the time to see the indicator? That's the bit the worries me in terms of mic use.
On Android I can toggle the camera and mic OS wide, and per app. When I'm not taking pictures or a call I turn them both off OS wide using the quick toggle buttons. On iOS I can only find options to disable them per app which doesn't give me as much confidence.