Our dishwasher keeps its little screen on and blinking until you actually hit the on/off button, and we effectively use that as a cleanness indicator. We only turn it off after having cleaned out the dishwasher. So the off state always means dirty. On and full = clean, on and mostly empty = someone probably forgot to turn it off, easy to spot check.
The problem is when you have a dirty dish and assume that the dishwasher contents are dirty too (because usually we unload the dishwasher soon after it finishes). Then you put a dirty dish in, possibly making other dishes dirty. So you have to either hand-wash several dishes or re-wash the entire load.