Correct, though PS Doesn't go Stby unless the flight is full, they can assign seats at time of booking, though as a rule they shouldn't. If the flight is full then they are placed on the oversold list (after all rev customers, elite upgrades included) and are the last to clear before any stby pax since they are a confirmed ticketed passanger. If the flight is overbooked and volunteers are needed they must declare themselves a must ride and a follow up is done with their superiors.