Reason two, they have have been tutored to give the right answer.
By way of example; the temperature gauge on my Audi (read any other VAG car) is driven by a stepper motor, whilst giving the appearance of a graduated dial face, the programming for the instument reads accurately from cold to the lower bound operating temperature, then for all temperatures in it's normal operating range the needle shows rock steady on it's mid point, only once the temperature goes above the upper bound of the normal temperature does the guage show movement again. Thus the gauge acts like emission tests, it performs in a manner we wish to see.
I would suspect that the Ford ECU is providing a similar service in order that any proud owner isn't unduly distressed by the sight of a fluctuating needle.
that's not how the ARP4 temp gauge works .. it does change according to driving conditions as noted above
