As far as I'm concerned, Galvan is hyping a non-issue. As I read the code, ANY 5/8 piece of steel or iron may be used as an electrode- even pipe or structural iron.
I think you'll find that stainless steel is not as conductive as "regular" steel.
I have had concrete workers claim that rebar isn't galvanised because the zinc damages the concrete as it decomposes; I have seen zinc deteriorate quickly in concrete and alkali soils.
I've always wondered why we just don't use #5 re-bar for our ground rods- and save the $$$. (After all, re-bar is the basis of the Ufer grid).