Yes, that is important to clarify.  You'd think people would automatically get it, but we weren't their educators, so it is what it is.
If you use any effects like that or your original art was glitter, lace, sequins or whatever, make sure to state that it is a sparkle effect, sparkle-like or somthing to that effect to let them know they aren't getting the original or real thing.
That might not help everyone as some people will only see what they want to see, but at least you will be covered on your end if they come back with the old, "you didn't say!"
Best always, Randy