those appear when you command reverse thrust, but i think the most common situation this is going to happen is when maintenance does sloppy work and something goes awry. in this situation, are your indicators still going to show up? and if you've got no indication, are you going to be able to diagnose what the problem is without that indicator?
as you say, the loss of control and utter lack of time you have to solve the situation before it becomes unfixable is a little unnerving.