The rule would apply with respect to the employee getting the car as a consequence of their employment. I think in the situation that you described, in which a father is providing a car to their child, it wouldn't be reasonable to conclude that the car is being provided as a consequence of employment.
If you have a situation in which a third party is providing a car to an individual and there is no link between that third party and the individual or other separate business reason to think they'd be providing that car, then I think that could be an indication that if there's some connection between that third party and their employer, then that car is being provided to the individual as a consequence of their employment. In practice, I would expect there would be conditions in place such that the car could be used only so long as the person was employed or that the car had to be used in the course of employment. I think facts like that would indicate that a car was being provided in the course of employment.