Says who, You?
Mice and rats gram per gram are the same nutrition until actual studies are conducted. Whether the snake is eating mice or rats it dont matter so long its eating. No one here has done exclusive studies to prove one is better than the other, but visual refrence.
Mice are closer related to ASF than rats. Rats arent even a natural food to them as they have distinct smell. Which is why a good portion of Ball pythons dont switch