I’m not sure that the use of “Indian” to describe indigenous / first nations people is settled or monolithic, at least given these two groups nearby me, where “Indian” is officially in their naming:
It could just be a legal holdover. I’ve seen this topic discussed recently here too:
As a basic white-guy, however, I won’t take the thorny position that it’s okay to keep using “Indian” to describe people who aren’t from India. Obviously, if it’s distressing to someone, especially given the history, why choose harm?