Why would a digital Yuan (or some other national currency turned into a CBDC) "help fast-track international settlements" in that currency?
How China Influences the U.S. Dollar
https://www.thebalance.com/how-does-china-influence-the-u-s-dollar-3970466

For export transactions to United States companies/consumers, Chinese firms typically receive dollars as payment for their exports. These firms then deposit the dollars into local banks, in exchange for yuan, which can be used to pay their domestic workers and vendors. The local banks then send the dollars to China's central bank, the People's Bank of China (PBOC). The PBOC holds the dollars in its foreign exchange reserves and regularly adjusts these reserves by buying or selling dollars via foreign currency markets in exchange for yuan.
By stockpiling dollars, the PBOC reduces the supply of dollars available for trade, putting upward pressure on the dollar and downward pressure on the yuan. By selling dollars, the PBOC effects the opposite result.


It is important to note that the PBOC does not sit on cash reserves. It uses the dollars it accumulates to buy U.S. Treasuries, which are safe-haven assets that provide some incremental return over cash.

The Same Problems Plaguing the Yuan Will Plague China's Digital Currency
https://qz.com/1899402/why-chinas-digital-yuan-wont-internationalize-the-renminbi/

Because the digital currency is little different from the yuan itself, it will on its own “not be a game changer that elevates the renminbi’s role in international finance,” wrote Eswar Prasad, a professor of trade policy at Cornell University, using the currency’s official name. “After all, the Chinese government still restricts capital inflows and outflows, and the People’s Bank of China still manages the renminbi’s exchange rate. Neither policy is likely to change significantly anytime soon.”


What investors are looking for in a reserve currency isn’t the technology—it’s a currency that’s stable, underpinned by a strong economy, freely convertible, and able to be used widely.