The video isn't working for me so can't comment on the finer details. However I fly the 757/767 and have been lead to believe that the 747 autopilot/mcp is of a very similar design.
In my experience, VNAV just becomes a bit klunky below 10,000'. It is less able to anticipate ATC instructions (and how can it, when have you last flown the plate?) FLCH just gives a nicer feeling for the pax and greater control for you as pilot.
VNAV is great for climb/cruise/initial descent, but lower down our brains are just better computers. If we could programme the winds exactly and fly the full arrival everytime, VNAV would be perfect, but that's not real life.