It's proprietary software. You can't know what they're actually doing without getting a job there and getting assigned to that project. But given Facebook's long history of user hostile behavior, the statements from Zuckerberg that people who trust him are idiots, and the class action lawsuits against them for violating consumer trust and straight-up selling user data, I wouldn't believe anything they say. Why use a 3rd party app run by a user hostile company whose entire business model revolves around capturing user data, when there are better alternatives out there? I understand that I'm preaching to the choir and I apologize. I've had the same argument with my two best friends trying to get them to use literally anything other than Whatsapp and they won't. So we still communicate with a group sms on our phones. That's better than Whatsapp as far as I'm concerned. You have my sympathies since your group is probably too big to just refuse to participate in and still get communications from.