Yea, if nothing else the Plaza accord tells us that exchange rates and trade deficits are fictional. Nixon floating the currency in 71 was because fugazi forex was looting the gold, since then it's everything else getting looted.

There's probably other hooks into these deals China makes like trade policy that might make the cost worth it to them, there's undoubtedly a currency war happening as the tariffs illustrate so it could be a simple matter of creating RMB demand at all costs to stave off a larger margin call.