Q: How do you tell that a Facebook spokesperson is lying? A: Check to see if his lips are moving.
Facebook has demonstrated on numerous occasions from the earliest days of the product that it holds user's privacy in contempt. What else do you need to know?
They really hate to be called out as creeps and liars.
I would update it as simply "Actions speak, words don't." Perhaps somebody can come up with a more pithy version. But it's amazing the amount of BS that you can cut through with this metric, and just how unbelievably worthless the torrent of words coming from our politicians and businesses are. I mean, worthless on a philosophically profound level. Astonishing amounts of effort are burned on ensuring that words are as disconnected from reality as possible.
Facebook will say whatever they think will advance their agenda, only very loosely constrained by laws and with many educated people who know exactly how to skirt those laws with precisely-constructed vague statements that sound like one thing but legally say another. (The easiest and most popular are statements carefully qualified to in fact say nothing at all.) Meanwhile, their actions are clear as day: Track everything, expand their tracking as much as possible, and worry about the details later.