Ultimately, it is about TRUST & CONFIDENCE in a mere piece of paper called the dollar, regardless of whatever national denomination it derives from...
China may had sold its stock of US paper denominations, but ULTIMATELY, what is confidence lays, in its ability for sane Humanity to BUY such precious stocks. Such did not wavered, & in a FREE market like US that adopts, MANY of Humanity WISH China would sell more...
Also, Aunty Yellen would have a bigger headache, as such purchases by Humanity would come with a cost - bigger saving interests to pay out to investors, & fortunately, those treasury notes bought by China was years ago would carry smaller interest rates than today, to be paid out.
With the meagre ROI ( returns on investments) with China' s action, would it solve China's economic growth?
That is yet to be seen as it's unregulated CCP derived policies upon its own national banking systems which saw hard earned saver deposits seized or corruptly used for itself or CCP officials run away with such funds, or CCP State run companies presuming money drops from the skies & thus frivolous spending with even such funds from the govt SIDELINING into the corrupt officials wallets...