As far as this hardware selection, you can do anything you want. You obviously have a disagreement with someone over this choice of hardware being used. (I don't know if you agree with this choice or don't agree. A good obfuscation to get a proper answer.) To settle your disagreement you require a sound, well reasoned engineering perspective on the compatibility of these two materials in your yet to be specified environment.
Now as far as your own ability to coming to a sound, well reasoned engineered choice. A choice where you fully understand the chemistry and mechanics of stainless steel hardware on galvanized steel, lets look at the evidence. You obviously have access to the vast resources of the internet. You are here and have asked us to solve your problem. Our answers have included an unreferenced but reasoned answer (that may or may not be correct) and a selection of a cited reference table that requires you to interpret the answer. After being given this information and with all of the additional services the internet can provide you still ask us to solve your problem.
I'm sorry to say that we cannot help you with your real problem. The real problem is that you cannot support your side of this disagreement with a well reasoned explanation when resources and answers are provided.
"A good scientist is a person with original ideas. A good engineer is a person who makes a design that works with as few original ideas as possible. There are no prima donnas in engineering." Freeman Dyson