Seriously??? What would you like us to say? "Controlled delivery's never happen to PO box's, ever!"? Or "You have a .0232% chance of a controlled delivery to a PO box"?
Logic would suggest that a controlled delivery to a 24 hour PO Box would be less likely than a home delivery, right? Considering they'd have to wait until you came to pick up the package vs deliver it straight to your home/office.