So this picks the short term income mobility, the picture is titled "Share of people remaining in the bottom fifth of incomes after four years". It's interesting for sure, but it takes some thinking to interpret in relation to usual intergenerational mobility measure. For example: UK is known for its thin social safety net, so income drops and hikes are hard and steep, and Denmark is known for its short but generous unemployment compensation - again leading to steep short term income changes.
(Also, the OECD's own press release on the article's source publication doesn't raise the same points and points at the Nordic countries as good models: https://www.oecd.org/newsroom/action-needed-to-tackle-stalle... - maybe economists, or OECD economists in particular, think that inter-generational mobility is a better measure?)
https://www.epi.org/publication/usa-lags-peer-countries-mobi... shows that sweden, finland, norway also have good mobility (behind denmark though).
edit: see also https://www.oecd.org/centrodemexico/medios/44582910.pdf - it's in the 1st page abstract.