The point is that you can't just externalize age verification and expect that data to never be sent to facebook because facebook needs that data to do anything (good or bad). It doesn't matter if your OS broadcasts that your child is 6-9 to facebook or if facebook has to ask the government to tell them that same information, either way, in the end facebook will know that your child is 6-9. The power is then in facebook's hands. Facebook won't see a copy of their government issued ID, but what difference does that make when they've got their age, their selfies, and a list of every friend and family member.