Imagine getting sick, or having a baby, or taking time off to care for a dying parent. That is exactly the kind of leave the law says is yours to take. Now imagine a computer program was quietly counting your keystrokes the whole time, and it held every one of those days against you. When the layoffs came, that program is the thing that decided you were the one to cut.
Here's why that's a big deal: a company is not allowed to punish you for being sick or pregnant or caring for your family. So when Meta says the people made these calls and not the AI, that only holds up if a person actually did the choosing. If the machine ranked everyone and a human just clicked yes, then "a person signed off" stops being a defense and starts being the evidence. This is the case that decides whether "the algorithm did it" protects a company, or convicts it.