It doesn't show up in their data, because they cut off at 0.1% - the hump is slightly higher than that. This shows where it was as of 2014.

https://www.taxpolicycenter.org/taxvox/how-capital-gains-aff...

I'm not sure where it is today, exactly. But it's easy to see that it's always going to be there, simply by virtue of increasing proportion of capital gains at higher income levels.