That's weird; every time I've been to a restaurant that uses Merchants as an acquirer the terminal pops up a currency choice prompt. Now sometimes I've had to use a bit of social engineering to get the right currency chosen (sometimes the employee tells me that management requires them to select DCC and in such cases I raise a fuss until my slip is voided and redone in RMB and on future visits I hold out my chipped card and pretend it's Chip+PIN, holding onto the terminal until I've chosen RMB) but it's nothing weird like the others- you get a very obvious "1 for RMB, 2 for other currency".