It doesn't cost the Chinese treasury anything except RMB¥ to discount its exchange rate - and that's not something that it runs out of the ability to produce, after all.

And its peg is to a basket of currencies, and they do not reveal the composition of the basket or the pegged rate, so they could definitely reduce the weight of the dollar in the basket but manipulate the peg to mask the move - where you would notice it is not in the exchange rate data but in the foreign exchange reserve data.

I've been accused of being a Marxist, yet while Harpo's my favourite, it's Groucho I'm always quoting. Odd, that.