I think it has more to do with the milestone of connecting Australia to the UK non-stop.
There were several milestones in commercial aviation history, like the first Pacific crossing below the Antarctic circle, or the first non-stop East-West crossing of the US, etc etc. We know the time and distance is not the real issue, it's the simbolic significance of what has just ocurred.
...Now, I bet the pax and crew must be barely alive.