Here is another opinion. Based on that label it does not need any extra additive. I have read here that the newer synthetic oils also do not need any extra additive.

If you are just adding a bit to your diff, then probably with or without would be fine. There are too many variables for anyone to say conclusively if it matters or not.

If you want to be perfectly safe, call Valvoline. I wouldn't sweat it unless I was completely filling a differential with it.