Yes, I know that, but most users wouldn’t know or wouldn’t follow that because it’s inconvenient. But I don’t agree with this solution for this particular case.

Yes, I know that, but most users wouldn’t know or wouldn’t follow that because it’s inconvenient. But I don’t agree with this solution for this particular case. It is a good practice in general. In this instance, nobody would expect that an app that you gave camera or microphone access to would be recording video or audio without you explicitly initiating such a recording. Imagine if WhatsApp was found to be recording audio all the time while you were reading chats or responding to chats in text just because you gave the microphone permission to it since you use it occasionally to send voice messages to certain people. Would that be acceptable, bug or otherwise? Why should one’s reaction be any different for the Facebook (or any other) app? What’s happening here is a serious violation of trust and expectations.