I noticed that this became more and more common back when ACA was passed. It's cheaper to hire a lot of people part time than it is to hire fewer full time people because of the benefits they would be required to cover
It has definitely been a trend at the public entity where she works. When full time employees leave/retire, two part-time positions are created to replace that person instead of hiring one full-time employee.
Since health insurance is 20-30% of the benefits package it’s cheaper to either hire under the full time bar or work people 7 days a week 10hrs a day and just pay the overtime differential. I think the calculus has swung enough that overtime at 1.5x is actually cheaper than adding new employees.