It creates confusion too. Twain sometimes used the word “slave.” Now one can’t tell where that happened. Also in that era, free Negros were sometimes called n*ggers because of the racial biases of the time. I think many a Negro of that time would turn over in his grave at this new lack of candidness about his situation. To forget history is to be doomed to repeat it.
But that would contradict the assertion that all black people back then were slaves. ;)