Why would heating salt in a pan prevent food from sticking?
Most of the described method will help you to clean and dry your pan. A clean pan, especially when it is cast iron, is a happy pan and will work better. A clean and smooth surface, and rubbing salt on it will clean and smooth a metal surface, will also help to prevent food from sticking.

Sprinkling your pan with salt immediately before frying fish or meat is pointless. What salt does to food is to bind water and less moist things stick less. But your pan should be so hot that the little salt can't make a difference. If the salt has time to dry your food, your pan just isn't hot enough.