There's nothing mysterious about whiteout. It is simply the eye having nothing to focus on, a special case of empty field myopia. If there's poor light under full cloud over ice and snow, you would still see a large-enough dark object. If you can't, it's not VMC (day) - by definition.
Collins didn't see Erebus for exactly the same reason pilots in VMC don't see the nearer snowy ridge when there is another higher snowy ridge behind: No contrast.
Whether or not Collins was in VMC as defined by the company, and thus required legally under CARs, is an other matter.
I have already broached one aspect of VFR with the CAA. It is that whatever the rules are about visibility and cloud, there is an implicit requirement that you fly with reference to the ground. In my opinion this should be explicit in the rules. In general terms it means you recognise the ground for what it is, preferably identify it. If you are above cloud then you must be in clear air such that higher ground or its cloud cover is obvious.
The fact is Captain Collins, flying VFR, descended without identifying his position with reference to the ground. He couldn't see a very large mountain he knew was close by, either above the cloud or below it. That is not a good position to be in. A prudent pilot might have retraced his path out over the sea and climbed. So confident was he of his instruments he continued. Under VFRs he was not permitted to do so.
I know Brian Abraham is, quite rightly, more concerned with the lessons to be learned than apportioning blame, but the sad fact is a large number of people out for a joyride were killed quite unnecessarily and I don't think the lessons were learned. That is why I brought up Perpignan.
If airline pilots are not going to accept the ultimate responsibility for the safety of the flight, why have them at all? Why not just program the aircraft and send it on its way? After all, it's probably at the point you really only need a pilot when something goes wrong.