Append the Boundaries and Relationships section of Citation Resource description page with:

"The Provenance Resource is used to track the contributions to a resource as it occurs,  especially for purposes of confirming authenticity and trust. Citation.citedArtifact.contributorship is used to report the attribution of contributions to the cited artifact, especially for purposes of recognition and acknowledgement, but is not  directly reporting the data to support authenticity of the contributions."

Additional comments regarding this change (in response to request from the FHIR Management Group):

At an element-level review, Provenance Resource includes a target element for direct relation to the target resource the provenance data is about. Citation Resource is not a direct fit for the target of the Provenance Resource (unless reporting the provenance of Citation Resource development). When there is a desire to report provenance for the cited artifact, use Provenance Resource. When there is a desire to simply report the attributions (which may be data transferred from others without provenance metadata), use Citation Resource.  

When Provenance Resource data exists it can be used to create Citation Resource contributorship data. But it is impractical to generate Provenance data for millions of external artifacts for which we will create Citation Resource data.