A buyer can file an INR case immediately after paying for an item...
A SNAD case can also be filed immediately (in next minute) after paying for an item....
If the buyer files and INR, then eBay calls seller and ask them to provide the tracking info. The eBay exec. will verify it and then close the case in seller's favor if the item is shown as shipped.
If the buyer files a SNAD, then the buyer has to ship the item back to the seller and provide the tracking number to eBay. When the item (returned item) is shown as received by the seller, then eBay closes the case in buyer's favor.
Whether it is PaisaPay or PayPal, the buyer can file an INR or SNAD case, the very next moment they make a payment.