That is a very stupid suggestion, as others have stated, due to fuel dilution and extra wear and tear, every 5-6 hours for no good reason.
If you have a good quality battery with plenty if cranking amps (not the bare minimum required), the coolant is good enough to not freeze over, the oil is thin and strong enough to flow when needed, I don't see why the car wouldn't start after sitting for a whole day without being harassed.
Idling for 10-15 minutes in freezing temps won't create enough in the engine bay to really benefit anything. With such cold temps, what little heat is created in the engine bay will quickly get attacked and freeze over within an hour, resulting in everything freezing again for the remaining 4-5 hours until your next planned engine start. Where's the benefit?