I'm at the Shanghai Brewery (Hongmei Lu location) right now, and just paid my bill.
When the DCC slip was printed, I requested a void, and was prepared to walk the waitress through the "cancel" routine during attempt #2, but during attempt #2, I saw that these new 银联 POS machines actually have a DCC (1. 是, 2. 否) step. The waitress told me that UnionPay and her manager advised her to always select option 1 because it is better for their foreign customers. In any event, the new UnionPay machines are really easy to beat if you take matters into your own hands.