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 a permission system as coarse and disempowering to users as it is today. I guess the people clicking the downvote button misunderstood.
I don't know what you mean. Existing behavior does not provide the control or visibility that I described.
One important difference is that the "permissions" in the screen shot are effectively all-or-nothing: if you don't agree to all of them, then you don't get to install the app. They're not permissions so much as demands.
(Some OS do have settings that will let you turn them off individually after installation, but this is not universally available, is often buried in an advanced configuration panel, leaves a window of time where they are still allowed, and in some cases have been known to cause apps to crash. Things are improving on this front with new OS versions, but doing so in microscopic steps that move at a glacial pace.)