Remember, this isn't the churn rate we're talking about. It's involuntary separation. I'd imagine the annual churn rate is way above 10%. I don't doubt FedEx and UPS have high churn rates, but I also suspect they don't fire 10% of their package handlers annually.
That 10% fired doesn't adjust for churn tho. Over the course of a year there were at minimum 2500 employees working there, we don't know how many unique people worked there over the course of a year to find out their firing rate.
I work for a mid-size manufacturing company, and we fire (or they quit) way, way more people than we keep
UPS does a lot of seasonal hiring during Christmas. This includes workers in distribution centers as well as helpers on delivery trucks.