True but when it comes for a voucher the person can use it and Reject the deal
as i recall escrow mainly work to provide the acc\vcoucher and person just need to check and accept the transaction , but in this case he can copy it and reject it ! and then i lose the voucher and to get back and cancel it will take dayss if not months
Alternatively as already suggested above I think it would be better before you send the voucher ask the buyer that your voucher is not refundable unless he has video proof that the voucher does not work. And then ask the buyer to start recording a screen video before sending the voucher until redeeming.