I picked up a 50s Prime Time reservation this morning about 30-45 minutes before the reservation time when I was at HS. Last minute pickups can happen.
And that's likely due to the fact that WDW allowed someone to cancel last min without a cancel fee. Because most likely that time slot would have stayed as a confirmed booking until 15+ mins AFTER the ADR time before it becomes a NO-SHOW.
Who lost in this situation, the guest who canceled, Disney or the new guest who got the last min ADR?