Import OrgAccount contacts creates default "Direct Contact" relationship

Ron Coscia 2

While importing contacts for organization accounts, a default relationship of "Direct contact" is created.  It does not, however, exist in the Relationship Detail Object, so you cannot modify/delete it.  Subsequent imports of relationships simply add another relationship for the contact (it doesn't replace the "Direct Contact" one).  Is there a document which explains the trigger that causes this? Is there a way to mass modify/delete the "Direct Contact" relationships?