Hi, Sam
A frost free freezer should automatically defrost itself,You are correct about some models using the cold air from the freezer to cool the fridge but the elements shouldn't have to be moved & if there is an exessive amount of ice on the freezer evaporator(part that makes the ice)them there is a fault because the freezer should defrost this ice itself.
www.candmdomesticappliances.co.uk, December 2009