Regarding products that are listed as "OK to be used on top of coatings", like CarPro ReLoad, I have been told this...
Overtime, certain contaminates can create microscopic voids in the surface of the coating. Think about a tiny particle of brake dust that has worked its way into the surface of the coating. When a product like Iron X is used to decontaminate the surface of the coating, the particle is then removed and there is a very tiny void in the surface of the coating. ReLoad (which is an inorganic water-based formula composed from specially modified Silica, glass nano components (5% total concentration)) can then be used to fill in those voids, thus rejuvenating the coating and adding to its life.