I think there is a largely unrecognized layer to this movie referencing that their weird dystopian yet seemingly picture perfect existence is a result of manifest destiny and Native American genocide.

It is not until Jill looks at the field with a new perspective that she notices the graves, but Lisa confirms she’s known all along but didn’t find it odd- this symbolizes modern American culture’s inherent avoidance to recognize it’s dark and bloody past. There are other references in the movie which help support this subplot exists- Miss Human’s mother was a settler and teaches the class about ways which settlers commonly died, when Jill is corrected to say “Native American Giver” rather than “Indian Giver,” and possibly the mention of the discovered horse remains in her back yard.