Why would Apple refund you for a service which you received in full? You got access to the program and a loan of Apple-owned hardware at the agreed price. [2] And now Apple is giving you a surprise bonus as an incentive to return Apple's hardware back to them. Nice.

You can argue that the price was too steep for a loan, or that Apple should be offering a more generous incentive to return the hardware. I wouldn't disagree. But it's not like Apple was unclear about this.[0][1]

[0] https://photos5.appleinsider.com/gallery/36365-67564-DTK-own...

[1] https://miro.medium.com/max/1400/1*V6If2OIL4W223oGLzT5OrQ.pn...

[2] To everyone who dealt with faulty hardware, I think Apple should be quietly offering refunds, not just a partial store credit. But to everyone else, they received the service promised by Apple in full and should be stoked at the $200 return incentive.