This happens because there are no black people of consequence in the ML pipeline. In my previous company Everytime we built a new model, a bunch of us would test it. Being the only black person in the company, I often found some very odd things and we would correct it before shipping.

I understand that fb is a much bigger scale, but all the reason to have a much more diverse set of eyes to test their models before they go live.

If you want to avoid this, hire more black people, seriously.