You are missing my point. I'm not saying the US government is correct, I'm saying no one else was counting the dead. And at the time, the US government had no reason to downplay the numbers since the voting population mostly didn't care.
And I don't have time to read your book, but I'm going to guess that the book relies upon the official government numbers and their extrapolates additional deaths based on some criteria. I doubt someone just magically found a new as yet undiscovered accurate death list.
A lot of work has gone into ancestry by the tribes and finding old records along with tribal sites not destroyed, but quoting old numbers without current research is just wrong.
And I don't have time to read your book, but I'm going to guess that the book relies upon the official government numbers and their extrapolates additional deaths based on some criteria. I doubt someone just magically found a new as yet undiscovered accurate death list.