Wrong. Their currency is pegged to the u.s. dollar at a rate determined by them. A falling u.s. dollar means a falling yuan, making them more competitive to the rest of the world. Meanwhile, selling our bonds they hold sends interest rates up because rates rise when bonds fall. Net, net, it hurts us and them.
I already said that it hurts us *and* them. But the point made in this article is that China is threatening to dump US treasuries because the US is considering taking actions that would force China to float the yuan.
There are things that the US can do via the WTO (with support from Japan and the EU) to force the Chinese to float the yuan...and they know it. That’s why they’re rattling their saber on this issue.