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?
It checks if the water is really truly out so opening the hatch is safe (as in no water coming out causing water damage). And for that it waits a time so the water has time to gather in the bottom.