How is GROUP_HASH_VALUE different from the hash of the parent document for a specific family?

Difference between use of Group hash value and Parent hash is as follows: 

Say Doc 1 And Doc 2 are same documents. 

Doc 1

        P1 -- (Parent Hash + hash C1 + hash C2 + Hash C3)

            C1 - Extracted and Ingested

            C2 - Extracted and Ingested

            C3 - Extracted and Ingested

Group Hash (hash of (Hash P1 + Hash C1+ Hash C2 + Hach C3)

Doc2 

P2 – (Parent Hash + Hash C1 + hash C2 + hash C3)

        C1 – Extracted and Ingested

        C2 – Extracted and ingested

        C3 – Not processed (child missing)

Group Hash (Hash of (Hash P2 + Hash C1+ Hash C2)

So, if we consider Parent Hash then the document would have been duplicate of each other whereas when Group hash is considered then both these files will be original.