A really weird moment for me was when I took away the ability from my phone to access my microphone from all apps, and yet when I say "Ok Google" the "Google" App opens up and then tries to ask me for Microphone access. I'm running an LG G5 with all stock Android and updates installed. It's a little creepy that an app with no access to my Mic can ask for said access when I say something to my Mic. My guess is the "Ok Google" functionality is at the OS level and not at the App level.

that's actually an optimization it seems, at the processor level there is a low power keyword listener for "Ok, Google" but it just fires the app it doesn't get anything more since you didn't grant it mic access.

A much crazier permission is phone access on Android. I recently noticed Facebook's Messenger had been uploading my call logs without ever mentioning it to me. Only realized when it recommended I call a contact back despite me not using messenger to call them - it saw the call in the phone's history and matched it against its database.