Yes, I was going to make the same comment. I enjoyed that benefit for many years when I used to fly UA with some frequency. It seems that QF do not hand out unsolicited seat-blocks.

On the other hand, U.S. and Australian airlines have opposite attitudes to seat-switching. U.S. airlines generally turn a blind eye if you unilaterally change your seat before take-off, whereas Australian airlines (Qantas, and also Ansett when they were around) generally react with shock and paranoia to that practice, throwing in a lecture about weight distribution algorithms. I remember once I took the wrong seat on an Ansett flight. When I realized my mistake a minute or so later I got up to move to the correct seat. Well, she was on top of me in a nanosecond, telling me that I had to remain in my assigned seat till after take-off! I don't understand why so many Australian FAs seem to think that the cabin is their little school room, but I guess it's because they've either been trained to think that way or they've not been trained not to.

Ironically, because of the laissez-faire attitude on U.S. airlines, even a blocked seat may not remain blocked. This happened to me once, where I was given an exit seat where there are only two seats (with a vacant space next to the door), and another guy just walked up from his assigned seat and took the seat next to me! When I queried this with a FA, she just shrugged it off.

Come to think of it, why do Australian airlines make a big deal about showing them your boarding pass as you enter the aircraft, and then telling you your seat is x rows down on the right or left? Once you've been through the boarding formality at the gate, why is a further check needed? And even if there is some reason for doing it, why do they cloak it with that silly practice of telling you the coordinates of your seat?