Hi msford;
electrical engineers at Ford tend to design scope around creating a fail safe system - in this case the radio 1 hr fail safe system is the battery - hence the battery management system that kicks in to save the person that forgets to turn off the radio only to find out they have a flat battery and now need either a tow truck or jump start.
Short answer is it is coded into the
BCM and
ECU; you will need to power "on" once the radio goes off but another hour of radio could push you to the limits and it may throw up low battery warnings on the dash depending which Mondeo series you drive.