A dirty lie, at least when it comes to "no waste", when you consider that the skin, head and tail of the fish, or about 1/3 of its edible tissue, is thrown away as garbage, and lucky if it's made into pet food.
This is the convenience and advantage of rearing entire generations on food that doesn't look like food: that they never wonder what happened to the rest of the animal.
No respect for an other living thing.