Will saltron mini or SWGs damage hot tub?

Hi, I was speaking with a sundance dealer and he said that an aftermarket SWG will void the warranty because it will essentially corrode and pit and damage all the parts. He said if I was really insistent on using one that I should wait until the warranty has expired. I read the Sundance warranty and do not see SWGs specifically mentioned anywhere, it just says essentially that water has to be maintained and sanitized.

Are his claims true? I see conflicting information online. Some say yes...

Will saltron mini or SWGs damage hot tub?