BNM is an editorial designation that is awarded distinct from the writer's album score:

Best New Music: Explained!
Q: How does Pitchfork's Best New Music system work? I've read reviews where two albums get a score of say 8.2, but one is BNM and the other isn't. --Aurora Nuncio
A: The truth of it is breathtakingly simple: Editors choose Best New Music albums based on the records that we think are the cream of the crop. These are excellent records that we feel transcend their scene and genre. When an album gets Best New Music, we think there's a very good chance that someone who doesn't generally follow this specific sphere of music will find a lot to enjoy in it.