Gates is wrong, as usual. The Cherokee did own slaves. There was even a slave revolt.
And ex slaves of Cherokees were considered members of the tribe until they hit the big bucks with land rights over the Arkansas river and casinos,,, then it turned into ‘sorry,you’re not on the rolls so you’re not one of us’
Yes the author was showing a lack of historical knowledge...which is far too common. Writers now seem to think they don’t need to be accurate. I always thought the hardest part of writing was the research, but they skip that step now, most don’t even bother with a 5 minute internet search.