It’s not a component aware system. The last phase is generally the spin cycle. The controller knows to trigger the spin cycle, it knows to stop the spin cycle after a period of time. What it doesn’t know is whether those things actually happened. Particularly, it doesn’t know that the drum has actually stopped spinning. So, it just wait a predetermined amount of time before unlocking the door.
In the case of my own device the door actuator uses a wax motor. Put simply, current is changed to heat which melts the wax, pushing a pin the locks the door. To open the door, current is removed, the wax cools, hardens and shrinks and the pin slides back. Now the door can open. So, even if I remove power during a cycle the door will eventually unlock as the wax cools.