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?

[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...