The functionality of Contacts application will Merge Duplicate contact information for contact information stored " On My Mac " and " iCloud " .
The definition of " On My Mac " being as the name implies, Stored On the Computer itself and iCloud as being the Apple Service on iCloud.
Now, when the Source of the Contacts information is also Synced to Third Party Services like Google - that will change things dramatically.
As a TEST ONLY, in the application Contacts, Untick Google from the Source to sync Contacts.
This will leave only iCloud as the one and only source to sync the Contacts application.
What happens ?