> Here he presents a few studies that go against general economic consensus popularized mainly by Piketty in "Capital in the 21st century" and through papers/writing by Krugman, Saez, Zucman, Stiglitz, etc. that most of the economic gains in the past 100 years have gone to a concentrated few owners of capital.

> Basically - absolute mobility (how much people gain over time) is still decently healthy today in percentage terms in the US, but relative mobility (how easy it is to move between classes) is widening and the wealthy in 1980 still have a much higher income on average than the poor in 1980.

These are not at all in conflict. As you say, the studies he discusses are not related to, much less undermine, any of the arguments that Krugman/Saez/Zucman/Piketty are making. I don't see any reason why individual characteristics like absolute mobility should be used to measure the health or inequality of an overall economy. Income mobility is a different thing from concentration of wealth or inequality.