I would bet that your instincts are correct here, but that they might not warrant a repair or service of the surface if you didn't follow their directions and add that stuff.
In any case, I'm confident that it's not necessary. It may be helpful in preventing calcium deposits on a rough surface, however. So, it may be good for someone who doesn't watch his water super-close. The more effective way to prevent scaling, I've found, is to keep Ph and TA in check...stops it before it starts.
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