Quote from #449: "For example, it solves the problem of working out the relatively few who are descended of slavery from the many who immigrated freely."
You have this reversed. I used to believe that ~90% of Black Americans are descendants of chattel slaves and ~10% of Black Americans immigrated here, when I looked it up a year or three ago. I was looking for sources and found the following. Whether it's 80% or 90% of Black Americans who are descendants of chattel slaves, that's still the vast majority.
https://www.pewresearch.org/race-and...re-immigrants/