Well I know that in Walmart when I've used my debit card in the past and have returned things, they usually give me cash instead of crediting my card. Maybe it's the same at other stores too.
With chip/pin cards, you would put your card in and enter your pin like normal but the transaction would be a credit. Then you accept the refund like you would a purchase. I imagine it would be the same with Pay, but instead you accept the refund rather than the purchase.