What is the point of that? Sodium is vital for your body so he is just risking hyponatremia for no good reason. Plus the body is really good at getting rid of excess sodium.
I started using "low sodium" salt, which basically is Sodium + Potasium, which both are electrolytes needed for the body. I grew up eating without salt (mom cooked with no salt at all) and using this low-Na-salt was amazing .
I know the parent said zero salt but ... that's hard to believe. In the modern world if you just breath you get salt in your diet. I bet if you try with all your might to get zero you probably up at the RDA.