When you own the bank $100, its your problem. When you own the bank $3 trillion, its the bank's problem.
In the same way, people with excel sheets think that China holds $3 trillion and that's it can do whatever it wants. However in the real world, Biden can change one entry in the database and make that $3 trillion "money" worthless or toilet paper.
So, China needs to offload these dollars asap. However this also that it has to remove dollar as the reserve currency and it needs to develop its internal market/consumption so that it can generate an even stronger economic gravity pull towards China and the RMB. All these require hard hitting economic reforms, which I am not seeing at the moment. It will take decades for this to happen