I have frquently refunded to a different card. For example, pay with Amex, refund to Visa/MC. Always the same payment method though, i.e. credit.
Merchants that insist on the exact same card number are just being awkward and don't understand the anti-money laundering regulations. They are there to prevent the 'production of clean cash' hence why a credit purchase should not be refunded to cash.
Years ago, I had to write a Stat Dec for QF to say that the credit card I had originally purchased something on was closed and the details of the new card they should process the refund to because they were insisting on the exact same card number. This example of where a card has been cancelled proves why the exact same card number is not necessary but just the same method of payment.