Observation from several slots earlier, re' ANZ's perception:
"... they thought they were being tracked on radar was because the transponder was coding at the time...."
The crews flying into McMurdo (annual resupply) were TRAINED to mostly disregard any position information offered by the local Navy-guys staffing McMurdo_radar. Also, due to repeated arrival-CFIT mishaps [turbojets while in radar-contact] during the mid-1970's, the TERRAIN-threat was a BIG training-lesson for any crew flying with a North American operator. An old-fashioned Pro-Navigator was aboard each heavy-jet landing at McMurdo, charts-out, constant challenging of any position-fix [mostly disregarding any info' from McMurdo-radar].
I recall flying downwind at McMurdo, with the ICE Rwy insight, and the only visual "horizon" were those ICE-CLIFFs at some un- certain distance, with the higher terrain obscured by low cloud.