Why aren't receiving tolerances and actions (reject for example) applicable to the distribution leve

Problem is that active encumbrance amounts do not clear due to over-receipt and subsequent overbilling (amongst other reasons). Below is an example:

1) PO encumbrance entry is created for PO's with multiple distributions per line and/or shipment

2) The encumbrance entries are created at the PO distribution level

3) PO receipts are at the distribution level and user over-receives on a distribution line

4) There is no way to prohibit over-receiving because the receiving tolerances and receiving actions apply to the shipment at lowest level

5) Invoice is matched to the distribution line and over-billed. The invoice will not go on hold because the invoice match tolerances do not apply to the distribution level.