JAN: The default returns bin should be set on warehouse level instead of org level. Org level is too high since multiple warehouses are possible.
PSA: The idea of putting it at org level is thinking that one organization can have multiple warehouses and you may want to have just one return bin common for all the warehouses that belong to the org. We also thought what you suggest and at this point we are still thinking which would be the best option. 1) In the information tab 2) In the warehouse tab