I think the site is reporting M2 for each of the currencies, which includes much more than just the bills + coins. E.g. the value of all USD coins + bills is "only" $2.1 trillion [1] vs. an M2 that's 10x larger. The 60% of all USD are held overseas statistic only applies to coins + bills and not M2 [2].
An explanation could be that people in Chinese save more and keep more of their savings in banks, compared to Americans?
An explanation could be that people in Chinese save more and keep more of their savings in banks, compared to Americans?
[1] "Currency in circulation" in https://www.federalreserve.gov/releases/h41/20210506/ [2] https://www.bullionstar.com/blogs/jp-koning/how-much-u-s-cur...