Facebook is over 20 years old and has never enforced its minimum age (13 years.)

I, for one, would have started with legal threats and financial penalties long ago. But it just won't happen. So I'm fine with technical solutions.

Facebook is able to sell you ads based on your favorite shoe lace colour. They ban terrorists, bots, porn and people named "Mark Zuckerberg" all the time. Noone can claim it's too hard for them to ban minors under 13.