Of course it would be very impressive if an university course offered a full refund after full completion of the course. Because it would require that the course has incredibly high success rate, and almost none of the attendees defect in this prisoner's dilemma.

Of course, if you get a refund from the course your qualification would be revoked and you would have to hand in your degree certificate. After all you are essentially admitting that you learned nothing worth paying for from the course, the university shouldn't be expected to lend its costly affiliation status symbols to people who didn't pay or learn something of value from their course.

A money back guaruntee doesn't mean letting the customer keep the product and the money (although that is a sometimes used marketing ploy). It isn't possible (or at least, not legally possible) to destroy the memories of what you have taught someone. It is possible to take back a piece of paper. This means that the impressive thing about a university that offered this would be that it implies that their pieces of paper are worth the price of the course even if you neglect anything students may have learned.