(yes, this job made you jump through hoops for a minimum-wage, part-time job), when in fact there weren't even any positions available. Don't ask me what this accomplished.

Other than amusing sadistic HR people, maybe it was a way to "trade up" in employees? Find someone "better" and fire a current employee, then give the new person their job? Maybe even for less pay?
Or sniff out potential rivals, see if they need to up they're game, my sister went through some thing similar for the company that did rune scape.