Not sure I buy that it does anything for you, but your pool already has salt in it. Think about it for a few minutes.

You add chlorine as either sodium hypochlorite or calcium hypochlorite. You add borax, or baking soda or other pH up chemicals. Thus you have Cl ions an Na ions floating around in the water. That is exactly what you get when you add NaCl (salt). These ions are all dissolved in the water. When you add salt you are adding more which may or may not dissolve depending on what levels you all ready have. You may actually create water chemistry problems, not to mention the potential for corrosion on certain metals. Don't think it a good idea.