That's why you need to open the dispute with PayPal!
The seller can't get you on a technicality they invented.
Open the claim, PayPal will say as long as you return it (TRACKING # Important!) you will get your money back. Whether the seller wants to or not PayPal will pull money from their account and refund you.
Open the claim, tell them it was false advertising, "the item is not as described". Escalate the claim to PayPal (allow PayPal to make the decision).
At this point you can even send an empty box, as long as there is a tracking number showing a package from your address to the sellers you should still get your refund. (Please do not send an empty box, that's just mean.)