Running on two cylinders and running a 'bit rough' are two totally different things, on two cylinders you will not have enough power to maintain speed and it will be so noticeable that I'd think even the rookie could not miss that...........however?
In my world people are taught that if they go ONE minute with temp solidly in the red they have just risked walking until enough money saved to buy new car. While one minute may not necessarily break it, I cannot imagine five. That programmed-in engine shutdown is an attempt to steer customers into dealer repairs, some engines will be damaged by the time they begin running on two cylinders. Zetecs are tough little engines but they run routinely and correctly at 230-240 degrees, by the time you register something is wrong the engine is already in engine damage from overheat territory. That little gimmick will not stop all of it..............
What I'm saying here is if you are relying on that feature to stop you from burning up your motor you are simply asking for it. When it happens you should have already been stopped and engine turned off.