I've only used them on chocolate and fondant/gumpaste. I'm not sure how they behave on icings. However, generally speaking, yes, you are correct in your thinking.
Oops! Once I used it on icing to mimic spilled champagne, I used the sparkle dust so that it would be glittery. But then I mixed it with piping gel and just kind of "spilled" it on the cake. It didn't react or anything. It did just what I wanted it to.