China wants the yuan to replace the dollar as the world currency.
Now think this out... If China wants to replace the dollar as the world’s reserve currency (NEVER HAPPEN), and kicking Russia off SWIFT is supposed to make the dollar not be the world’s reserve currency, why would China be taking this position?
Russia has been preparing for possible sanctions in the form of SWIFT exclusion since 2014. That was when it faced sanctions for annexing Crimea. It has set up a messaging system SPFS (which translates into a system for the transfer of financial messages), which works within the country. There are plans to integrate it with China’s Cross-border Inter-bank Payments System (CIPS). This will facilitate trade between Russia and China.