I have never seen my rear diff light ever come on while driving it. I have gone hours on a track day with it full rear lock and still never seen that light appear.

If you have it on full lock front or rear and not even driving it hard and you have seen the light I would get it checked t as there might not be enough oil in the rear diff.

The DCCD is still only changing the Center Diff but when on full rear it is sending more torque to the rear diff and not the front putting the rear under a bit more stress.