Z-Bar question regarding hole under clutch rod post

The extra hole is for models that have an interlock rod between the z bar and a pawl lever outside the case that meshes with the 1st/rev lever.
What Mopar used a reverse lockout as you describe? Not one in '64-'66, the years this Z-Bar fits. Trying to picture how it would work, so with the clutch depressed, it would stop the engagement of reverse gear? How does it know if the car is moving or not?