That's right. We don't need to add ANY salt, or even any herbs spices or pepper to dogs' food. They will get enough sodium in the meat and fish and vegetables in their food.
Potatoes are not bad for dogs by the way. In moderation of course, as no dog is meant to have potatoes or any other carbohydrate as the main part of their diet. Both white and sweet potatoes are fine and okay to include with their food! But never give them any green or sprouting parts of a potato skin! Those are toxic, (for humans too.) Always cut those off, and always cook the potatoes first. Never feed them raw.
I used to cook 'potato bread' for my dog, for the occasional treat (she loved it!) and it was ideal to put a tablet in small pieces of it, if ever she needed to take a tablet.
I boiled and mashed a potato, added a little organic wholemeal flour and a little fine oatmeal, and some olive oil, made a dough, and rolled it out fairly flat, and baked it in the oven until browned.