I consistently get them on 738 flights in Emerald City but haven't on the past few 734 flights (also in EC).
Don't think it has anything to do with load as both shadowed and non-shadowed flights were very full.
The second last 734 flight had an unallocated 5B when I arrived in the MEL J lounge just over an hour prior to departure - this I know because when asking the attendant to print me a BP I asked "is the seat next to me blocked?", to which the reply was: "It's not, but there is no one allocated in there right now", ie not a proactive "Would you like me to block it for you?". Said 5B was obviously allocated quite late then (boo, FWP).
Interestingly the 734 return had 4ABC allocated (me in 4C) however only 4D/F were taken... with the remainder of EC having all B/E seats occupied.
