Even if you had seen the movie, I think there's a real problem with characterizing it as "whitewashing" when there is difference of opinion among Indigenous scholars and when Scorsese consulted the Osage community and tried to represent their views, as did David Grann in the original work. This subtly suggests that all Osage must have the same view of their history, that they are not allowed to have the same diversity of views that we would allow ourselves. Why privilege a few scholars' views (which are questionable) over others in this case?

If the movie didn't take Osage suffering seriously; or presented the white men as saviors; or justified their justifications, THEN we might talk about whitewashing.

BTW, David Grann's book on which the movie is based is not a novel, but non-fiction. The site that you link in your piece describes it as "true crime history."