i don't see how the person taking in the parcel is under any duty to trot round to deliver it.
you have a strange way of looking at things, EP.
far from interfering in your transaction, the neighbour has been inconvenienced by having to interact with a delivery person, with no benefit to themselves, and then have the parcel hanging around in their premises, or the bother of trotting round to get rid of it.
it's ok where people are all equally helpful, i suppose, and willing.
but i wouldn't get involved. i don't want people coming to my door, or the responsibility of others' property.
then again i do not have any parcels coming to me.
a neighbour near me had difficulty getting his parcels from his neighbour. she would say she was in the bath, couldn't come to the door, or never answer the door, or just say she hadn't got his parcel.
he felt she was keeping them. the most charitable explanation was that she is not the full shilling.