That's interesting. I don't know the answer but I'd like to know it.I haven't read through the whole thread so if it's already been answered, please forgive me.
I was under the impression that many of the tribes of North America didn't participate in DNA collection. Apparently it had something to do with mixing of the tribes and therefore DNA, as well as tribal members not always being of Indian blood. Meaning if someone mixed or even white/brown/black/whatever was brought into a tribe, they were a member regardless of bloodline. Being "made" a tribal member was as much a spiritual and technical membership as a blood line would be.
Anyway, that is how I understand the lack of DNA samples in the database.
My DH, our children, his siblings, nieces and nephews, etc... are on the Cherokee roll. They all have their "blue" cards. They all got Cherokee Covid relief payments. His first cousin has lived his whole life on the reservation. They know who signed the Dawes roll and what clan they descended from. Yet when DH and DD did DNA tests, she was 0% Indigenous and DH was 2%. Now Cherokee doesn't require a blood quantum but it seems that it would at least show up.