I got hit by a Global Blue tax refund multi-currency conversion when I had the money refunded to my credit card. The refund amount was €14. Based on the posting date, the refunded amount should have been $15.80. However, only $14.59 got posted. That's a 7.658% worse rate than what I should have received.

Since it's not a true DCC situation, I don't believe there's a method of contesting the transaction. While getting the tax refund is better than nothing, there doesn't seem to be much of a way around Global Blue taking a cut of the payment. Fellow member percysmith indicated that even taking a cash refund is subject to a fee and isn't necessarily available in all locations. In my case, the cash refund fee at Helsinki Airport would have been €3.

Examining section 4.3 of the FAQs, it would appear that Visa, MC, and Diners get refunded in the currency of the card. China UnionPay gets refunded in USD and AmEx gets refunded in GBP, but I imagine Global Blue sets the exchange rate for both of these. JCB appears to be in local currency, but that's the only exception.