Why system allows to Match Invoice to a PO whose receipt is returned

Hi,

We are able to see the returned receipts in AP Invoice matching screen.

My understanding is that, once a PO is returned , then the same should not be available for matching in AP.

PO No. 100000

Qty: 1

Qty Received : 0   (receipt is returned for qty 1)

Still the above PO 100000 is available for matching in AP Invoice matching screen.

Could some one explain this please ?

Thanks,
Sunil