If your deck has a waterproof surface you will need a gasket system to keep the plywood substrate dry.
On the west coast where it rains a lot vinyl flooring membrane that is heat welded at the seams is quite popular. So are fiberglass coated surfaces. Ceramic tiles with waterproof grout and thin set mortar. There are EPDM surfaces and the list goes on.
In these cases if you are using a surface mounted railing system you have to think about how you are going to stop water from entering the screw holes.
Some places have real winters with freezing and thawing.
If you expect a lot water and freezing conditions during the winter, the gasket kit may be a good idea. Here’s why…
Water and moisture can track down along the concrete screw.
During freeze cycles this water will expand and exert immense force on the concrete. The concrete will eventually start to crack.
If your winters are dry or mild you will not have to use a gasket system.
Concrete is usually an uneven surface.
The rubber acts as a cushion filing up the gaps and also protects the finish of the anchor.
But the anchor is still galvanized and powder coated so it will still remain rust free anyway unless you really scratch it so hard you start do thin out the zinc coating.