So, under your scheme:

1. I sell a widget and notify buyer it's shipped
2. on day 5, buyer starts asking where is package
3. on day 8, package I mis-addressed is returned to me by PO
4. knowing it may take 4 more days to get to buyer it seems I might get negative feedback over this (and deserved)
5. So, I leave negative for buyer "never paid"
6. buyer can't respond or retailiate, and my feedback record shows I am a great seller who doesn't tolerate non-paying buyers