Hey all,
Don't panic yet. Yes, Haas does read through the applications with at least TWO (sometimes more) readers before extending an invite, which is why the invites go out later and come at random times. This is definitely a good thing since you know you're in a pretty select group if you get an interview.
The volume has gone up, but not as much for R2.
California invites usually go out last because of the ease of arranging travel to get to SS, so don't be surprised if you get an SS interview a week before the day. Also, California applicants can be interviewed on campus, so some invites have gone out AFTER SS. So don't give up hope yet.
What else... Pretty much even if you don't get an interview, it doesn't mean you're dinged. You may get waitlisted and interview after the decision release deadline. I've met quite a few R1 W/L who are interviewing in the past few weeks. I'm guessing many should get off the waitlist after 3/18 (R2 deadline).
Hope that helps!