Often with such systems there are irregularities introduced in the interaction to isolate key states in the range. The most obvious states are the beginning state and the end state. In some interactions these states are desirable for some reason and so are made difficult to leave. In those situations you may want the door open but not open all the way. Similar interim states can be found on some hi-fi controls.
Some British cookers pick out the simmer state in the range in a similar way.
These interim states are built in, based upon objective ideas as to which states are important to the users. But very often with such ranges the important state is purely subjective and as such cannot be built in. That is if they hadn't already blown the kitchen up.