No. "Element" in the article cited doesn't mean a chemical element or molecule but the it is considering the "volume of stuff" under consideration. The "element" could be a solution, the ocean, or a galaxy sized masses. Also heterogeneity/homogeneity are typically applied on a "macroscale" sample meaning large enough that the sample isn't quantum sized.
Thus for water (or some solution) the heterogeneity is really a concept of the volume of solution under consideration not the water molecule itself. So a liter of salt water would be homogeneous, but clam chowder would be heterogeneous.
If we were considering homogenized milk then yes/no gets a bit tricky. We'd have to consider how we define homogeneous since 1 ml sized samples would be the same but the homogenized milk really has two phases mixed together. (I'd guess that you could centrifuge homogenized milk and get it to separate.)
As another example the oceans are heterogeneous. The surface water will have a different chemical composition (pH, salt concentration) as compared to the water in the deep parts.