They do have to say "confites" (I don't know how to say that in English), they can't call them just "olives noires", but I didn't realize they could write "olives noires" on the package and say "ingredients : olives noires confites". That seems very dishonest.
But in Belgium they can just call them "olives noires / zwarte olijven" and indicate "stabilisator E579" in the ingredients, which I think is even more dishonest.