Why its needed to have a the AP bill and Debit Adj for Clearing the Purchase Receipt which is Already Returned

HI All, 

As per best practices  and its Normal and Simple  Process   as per my Knowledge across during the years the following is the Transaction entries which will clear the Purchase Receipt and return 

Purchase receipt 

Inventory Account  Dr.

Purchase Accrual Account Cr.

Return Before Invoice / Bill Created 

Purchase Accrual Account Dr.

Inventory Account  Cr

By this  both the account get cleared  and reconciled as well. if its Partial return Yes the balance remain  and  which can be cleared by Bill as its not retuned 

As per the Functionality of Acumatica we need to create a AP Bill and a Debit adjustment for any return ?? though both PR and return has been Processed both Transaction remain uncleared in the accrual Account 

why this is required  and the logic behind this Functionality ?