You can now select and pay for exit seating online on some flights. I can see this for a QF11 388 flight I have in January, but not for a 744 AKL-LAX flight, nor for QF133 MEL-AKL.

The available seats show with a red hue:



After selecting one you are asked for CC details to pay for these seats later in the process.

So this 7 day thing seems to be side-stepped.