The investigator assigned to my background check had to call me to get clarification on a couple specific items and although I can't recall the exact wording I do remember him indicating that he only had to call me because of those specific items and that not everyone does a phone interview.
Also, my recruiter had anticipated that it might take a bit longer for them to process my background check since I've lived abroad a couple of times and had a relatively complicated work history, and I remember him saying that it did not matter if my background check was approved before the board met, only that I had completed and submitted it before the deadline.
Edit: As far as it being processed before getting a ship date...I remember my recruiter saying something about that but dont remember what lol.