It's pretty naive to think this is the extent of it. They didn't make a billion dollars by sending people information about how much time you spent on the app. They analyse your chats and posts to see what kinds of things you're interested in so they can build a sort of 'person data structure' full of data points unique to you that they can package up and sell to advertisers.

This is just my best guess anyway, based on what I've seen elsewhere in the industry. It's safe to assume Facebook is hoarding any data about you they can legally get their hands on, including contact info, speech info, facial info, information of people who don't even use Facebook.. There's almost no laws for this industry yet, you can collect anything.