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 washing machine can be opened when running at any time so no idea what washing machines you have. Considering I want it to be going already when I add detergent.
Front-loaders usually restrict you from opening the door before they’re drained, or else some idiot would flood their apartment.