This is a good read on the topic, in particular this part:

But unlimited access to deep and liquid Chinese capital markets may not necessarily be essential for RMB internationalisation. Rather, the renminbi can acquire that role through its use in invoicing and settling China’s foreign trade and payments. China has established a global network of clearing and payments, such that it is now possible to undertake cross-border transactions in RMB in a wide variety of different jurisdictions. Our research shows that the development of the RMB as a reserve currency has kept pace with the expansion of trade invoiced in RMB, notwithstanding China’s limited capital account openness.

https://cepr.org/voxeu/columns/renminbis-unconventional-route-reserve-currency-status