I get it that China and many of their trade partners would like to distance themselves from the US dollar but there are reasons that so much international trade is done in USD over other available currencies. One reason is that the USA is a third disinterested party. If two countries do trade in the currency of either nation then the nation that controls the value of that currency has not only the motive to influence the value of that currency but a large lever with which to move that value. This ability to change the value could be so high as to render it worthless. Get a third party currency, especially one that has no real interest in providing advantage to either party, and that makes that currency more valuable to both parties in this transaction. The larger matter is that both agree on the value of the currency, and that it will continue to hold value with only modest changes in that value over time. Maybe one nation can give some high level of assurance that their currency isn't going to be devalued quickly, but I doubt that nation is China with some newly constructed digital currency.
I think this is the part which is the clincher. The US is not a disinterested party, and its strategic intentions with China are very clear, especially when the USA is doing everything it can to maintain alliances in Asia, to encircle and mount a capable naval blockade around China, so maintaining that the USA is disinterested in China's trade, well, I'm sorry but it's just wrong. In this context, nothing is necessarily being done because it's beneficial in pure business terms, but there's also national strategy behind it, so one would need to consider what is China trying to build from it?
The stability of the USD is due to consistent trade, but it has brought significant benefits to the USA and probably at the expense of other nations, since other countries need to obtain USD in order to enact transactions, while the US just sets its money printers to go brrrrr, and a huge amount of the USA's power really comes down to the value of the USD. I suspect that it's in China's interests to start to undermine that power, and start building up their own currency, to become a stable and viable unit for trade. When you consider the amount of trade China already does, and that trade largely resulting in propping up the USD, and not their own, they're probably keen to see that change.
In isolation, this may not make a lot of sense, for the reasons you point out, but in a strategic sense, with longer term goals, I think for China it makes lots of sense and probably should be a concern for the USA. But also to add a bit more context, I think we're also starting to see the peripheries of USA hegemony being tested, and some opinions are that WW3 has already begun. It appears like the US interests are being attacked at numerous fronts, with the goal of undermining confidence in the USA.