Don't quote me on this, and someone can correct me if I'm wrong, but the way I understand it is if you applied online, your case goes straight to your field office. If your entire file is there, they'll schedule an interview, otherwise they have to get your file first. If you sent a paper application to one of the Lockboxes, your case gets moved to the local office sometime after the biometrics appointment is sent. When and how they do that, I'm not sure.