Most washing machines have a timer that prevents you from opening the hatch just after the washing cycle ends. Instad you must wait for the timer to go off, usually a minute or two, before you can open the hatch.
Why? Would letting the user open the hatch immediately after washing ends pose any safety or other issues?
My bet would be it’s waiting for temperature to drop.
Edit for the downvoting folk: Some of the profiles of my washing machine have temperatures of up to 90°C
I would bet that the water for the rinse cycle would be cold though.