That is not the situation at all. He was VMC laterally, but the vision ahead deteriorated - whiteout, surfeit of light. No different to the Commander, VMC laterally, but no effective vision ahead - black, devoid of light.
Megan, you are very quick to point out when you consider others are extrapolating from the facts; but you have no proof of your own statement above either.
We will never know with certainty what was seen out the cockpit window. But the point is this. Unless Collins perceived
exactly what Vette theorised - which was sky above, ice below, a horizon in the middle and a flat vista of land extending to the "horizon" ahead, (not to mention VMC conditions all the way during the descent) then his failure to immediately climb away at 1500' is completely inexcusable.
Vette's theory is highly speculative. It's a big leap of faith to use this to explain away a CFIT event which took the lives of 257 people.