Am Able to make receipt correction after AP match and payment for Standard PO routing.

For a Standard routed PO where the receipt is performed as a separate step from the deliver transaction-   we have discovered that a receipt  entry is able to be corrected after AP has matched and paid against the original receipt quantity.    The deliver portion of the transaction had not yet occurred.      Is this a bug, a setting or intended functionality?     

If a setting-  can someone provide the specifics as to where?

If this is intended functionality,  what is the reporting that is available to see this type of unexpected activity? 

Thanks.