I have had my sister on the wait list for syd-lax since the 21 days cuttof date. She just cleared to business class 11 days out. so it looks like they do try to clear the wait list before putting them in the pot.
BTW I hacve been checking every day and there is constant availability for 7 days then nothing.
I think if you check late 24th early 25th you will get your u class!!