That's true in Mainland China. From what I've read from our resident experts here is that it's a function of the payment terminals not allowing a selection after the quote slip has appeared. However, Taiwan will honor the currency selection on the quote slip. I've heard merchants in Thailand will too, but I haven't been to Thailand to test this out personally. I don't know about Singapore, but I'd assume they'd honor the selection on the quote slip too. If not, maybe imposing DCC against a customer's will should be punishable by caning.

In Taiwan the merchants where I've seen DCC have primarily been department stores, and they've always given me the final charge slip showing TWD. I have my wife explain to them upfront that I want to be charged in TWD, not USD, and they've always been able to accommodate. The only other place I've seen DCC has been at the airport Novotel. They force the room authorization hold to be DCC, but since this charge falls off I don't complain too much. I use AmEx at the Taipei Sheraton, and we book through a local travel portal, which doesn't use DCC since it's all Taiwanese using it, for all other hotels.