I’m fairly certain if you showed pictures of both groups to a toddler they’d be able to sort them correctly. It’s really not hard for a human to tell the difference. Which tells me that FB’s AI isn’t really that great.
I saw another article which included a screenshot of the mistake on facebook. The photo is blurry, and contains a side view of the person and iirc the backdrop is in nature. The main indicator that it was a person was the fact they were wearing clothing. Clearly the AI is not good enough, but I will admit that the data it was working on is tricky to achieve perfect accuracy.