We literally have wireshark and similar utilities available to all of us to inspect every packet of data coming in to and leaving our phones. You can install pcapdroid right now to see exactly what facebook is doing and where that data is going. This is not complicated stuff.

Now imagine the payday and notoriety that'll go to the security research firm that is doing this kind of work on a regular basis and is able to definitively prove it's happening. Why do you think that hasn't happened yet?

I believed they maybe weren't listening because those cases that people claim as "proof" of listening can usually be explained in other ways as well. People tend to assume they were listening because its the easier explanation but with the amount of data that Meta has, they can easily lead people into thinking about things by showing specific posts on the Facebook timeline and also predict to some extent what people may end up talking about based on things like how many times you replay a certain video and how long did you keep certain posts in focus on the screen and that sort of stuff that people often don't realize is also data for them.

Still, I would never put my hand on fire for them and never completely discarded the possibility of them listening.