Payment Protocol: Is using different addresses for refunds just because of privacy? One of the features of the new payment protocol is that it allows the customer's wallet to automatically send a refund address with the transaction to the merchant.

Why would the refund not be sent back to the same address?

I read the related question regarding why change is sent to a different address. Gavin and David Schwartz mentioned it being more difficult to track your bitcoin spendings and it obscuring which address is the spending address and which the change address. 

Is this the reason why new addresses are supposed to be used for refunds or are there any additional reasons?
Some hosted wallets are using addresses in elaborate ways. So you cant be sure the address sending the payment is the one "owning" the bitcoins.

An example is CoinJar, that uses addresses to indicate to what account the funds should be added. But behind the curtain CoinJar does anything it feels is best, making the most efficient use of all its previous outputs.