Interesting points (skip to the 32 minute mark of the video to jump to the conclusions section):
The oil gets contaminated with water if the filter is not pre-filled with oil prior to installation. This happened with both the 5W-20 and the 20W-50:
The thin oil shows increased wear because of this contamination:
The thick oil, even when not pre-filled does not show increased wear:
In all cases the thicker 20W-50 oil offers MUCH more protection than the 5W-20. The thin oil exhibited increased iron in the oil in every scenario, and in particular after doing a power run on the dyno had 61ppm iron, compared to just 21ppm with the 20W-50. The hosts said that this mean the thick oil is giving 4x as much protection as the thin oil (or perhaps that the thin oil is showing 4x as much wear as the thick oil. I didn't question the maths).