Having an indigenous great6 grandparent must be extremely common among non-indigenous North Americans with a couple of centuries of settler roots. I probably have at least one such ancestor (my first known European ancestor on the continent came to New France almost 400 years ago), but even if I could prove it I wouldn’t dream of identifying myself as indigenous.
Warren’s “family lore” has a place at dinner parties and family reunions, but I don’t see any place for it on official paperwork or in politics. She may not have been the one to introduce it to the political arena, but she did so indirectly by listing it on paperwork.
A small error in judgment – but why?? – that has become a large error in judgment, on which she’s doubled down by claiming that proving a ~6 generation link makes her the winner of Donald Trump’s stupid bet that nobody sensible would expect him to honour. Technically she’s right, but does she seriously not realize that it’s a no-win game and nothing good can come of it?