yes common.
It is common because you can no longer get real reef rock except from a few places.
This is all fake painted stuff. As you can see... it is very convincing.
Coralline shouldn’t grow on the bottom of a rock so I would just flip it over and look at your original one you posted. I never bought the fake stuff but I would assume it is painted on all sides.
I looked at it closely. I think you're right. It's painted with real coralline algae growing on it. Does having painted rock impact water quality?
The Reef Rock, which ironically was cheaper, is definitely real. Has little worm tubes, swirly thingies growing on it, but looks critter-less as well.