I recall watching an episode of Engine-masters (your link as I recall) that claimed 30hp loss for a solid fan vs about 1hp loss from additional drag at the alternator so I would agree that its a reasonable assumption, leading to about a 29 horse power reduction in parasitic drag resulting in Better Performance, Efficiency and reduced emissions. But I would rather know than assume. I haven't seen any data for how much drag it takes to turn a 6v generator vs a 12 alternator both under load and free spinning.
All things being equal you can assume producing 12v take twice the drag of producing 6v AT FULL LOAD. But then there is the difference in technology. Better Bearings, Lubricants, Electronics, etc. also Running a 12v system that only pushes 6v could be more efficient than a pure 6 volt system etc etc etc.
but it seems to me just spinning a 6v generator and a 12v alternator out of the car take about the same exertion of power (not alot)
anyway, I am sure I had a point at the beginning of this, but its lost on me now. so just casting out lines looking for information. Thank you all for your input!