i don't think its really much of a benefit. they do it because when you delete your 4ws you are left with capping off the fluid came from. by switching to a 1g rack you eliminate those. they want to make it like the car was never 4ws as the 1g's were not(deleting the 4ws completely and correctly).
not sure if that is all the reason but i know that somewhat is.
hope that helped.