On September 2, Shanghai International Energy Exchange (INE), a subsidiary of Shanghai Futures Exchange (SHFE), has released the amended Clearing Rules of the Shanghai International Energy Exchange and Delivery Rules of the Shanghai International Energy Exchange, formally accepting Chinese government bonds as margin collaterals. The two amended rules will come into effect on October 18, 2021. more from here China INE to Accept Chinese Government Bond as Margin (qmhedging.blogspot.com)
So that could be part of why BlackRock likes china bonds more these day, as they can hold china government bonds and use them to leverage up their futures positions in China