if you record a video with sound, then the FB app has to have permission to record your audio.
I can’t tell if you’re trying to explain how it currently works (which I know very well, thanks) or asserting that the current behavior is necessary in order to record with sound.
It really doesn’t have to be as it is. The OS can provide a record-video API, complete with a user-controlled kill switch and an activity indicator, and the app can call it. The app doesn’t need direct access to the microphone to allow the user to create a file with sound.
Edit to clarify: I’m not saying that the “permission” doesn’t work as advertised. I’m saying that recording an audio file doesn’t have to require permissions as broad and disempowering to users as they are today. I guess the people clicking the downvote button misunderstood.