https://thefederalist.com/2017/07/03/china-secretly-manipula...
China was keen on strengthening the yuan and were doing that for a couple of years, but the trade wars have shifted their calculations. The earlier strengthening gives them some additional leeway.
I think the reason for this drop in the exchanges is because letting the yuan drop is China’s way of saying they’re in for a fight. A stable yuan was basically a precondition for trade talks, and this coming right after the last round means the hope for a resolution seems remote at best.
I still don’t understand how China expects to win the trade war. The US has a lot more firepower. But I guess leadership incentives are not aligned with the country and it’s peoples incentives (which is true in the US as well).