Malcolm,
If Captain S. was told that the nav track went over Erebus, then Jim Collins was told that the nav track went over Erebus - because they both attended the same breifing.
If Jim Collins was told that the nav track went over Erebus, then it was a clear-cut case of pilot error.
If it was a clear-cut case of pilot error, then NZALPA are full of sh8t, and have been so for the past 30 years.
So you can see why there might be some resistance to the suggestion that Capt. S. was told that the nav track went over Erebus.