Good for them seeking to preserve their genetic and cultural heritage.
Maybe not in the way you are assuming.
By way of example, in the St. Regis Mohawk tribe, to be accepted as part of their genetic and cultural heritage it is necessary to prove that you are at least 25% Mohawk.
This in itself is rather interesting since the Iroquois (including the Mohawk) had for centuries made a practice of adopting the women, children, and young men that they captured, and in addition to that, because of the matriarchal nature of their culture the children of any Mohawk woman were also considered to be Mohawk, even if the father was European. This makes the question of Mohawk ancestry even more problematic.
Other tribes are not quite so fussy. To join the Cherokee Nation you have to be able to prove that one of your ancestors was on the Dawes Rolls, a list of 'official' Five Tribes members ordered by the U.S. Congress at the beginning of the 20th Century. No blood quantum is specified.
The Eastern Band of Cherokee have the Baker Rolls (1924). They require a 1/16 blood quantum from someone on that list. That would be
one great-great grandparent.
Many native American groups don't even go that far.
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tl;dr
The point is, ST, I think you are being a bit too congratulatory. From what you have said in past posts it doesn't seem like the efforts you are lauding here would even remotely approach your standards of racial purity.
Or would you consider someone with
only one white grandparent out of all their ancestry to be white?