@henry crun, ampan :
I think they thought they were identified on radar, as the transponder was coding before the letdown began (and probably during to some extent) - and that the offer to descend from the controller confirmed it.
@prospector :
ANZ only sold the outer rows of the aircraft on the Antarctic flights in order to make moving about the cabin easier - you can see this in the various films and videos taken for promotional purposes, and by the passengers (including one from the accident flight which is very eerie to watch).
Will pick up the rest tomorrow.