If you want to be an evangelist, how about instead telling us the good news about camera gear that you recommend and are familiar with?
That would be a productive and positive contribution to the board. You now shoot 6x8 film and a D800 (maybe others?). The board would benefit from hearing about how you're getting the best out of both options, along with perhaps your experience with the non-gear side (production issues, working with celebrities, etc).
I don't really see any benefit to anyone (including you) to the anti-MFD rampage you've been on for a few months now. We get it; you think it's all a bunch of malarky.
As to the video --- as pointed out above, the user guide *recommends* stopping down when using the "fast" focus mode. It's not *required*, though it definitely increases your hit rate.
The reality is this is
advertising. If you watch a commercial for a sports car you'd be led to believe that it's perfectly acceptable to pull a U-turn in a desert at 60mph. Probably somewhere in the owners manual it will *recommend* you "stop down" the speed of the car when pulling a U-Turn :-).
I think it's fair to say that the good medium format dealers not only allow, but
encourage, customers to evaluate the equipment they are considering purchasing. We certainly do.
As to whether you can shoot in fast mode wide open. Here is my personal experience: If a wedding reception is outside or in a brightly lit room I will use medium format for reportage-style portraits of the attendees. I do this wide open in fast focus rear-button mode* (spontaneity and not being noticed or annoying is important to my desired outcome); focus is off on maybe half the shots. If it's in a darker environment I use a 5D3 with a fast prime lens in continuous autofocus rear-button mode, wide open; same thing - I miss focus on maybe half the shots**. I could easily stop down and increase my hit rate, and I could easily spend more time with the camera to my face to verify and tune focus as needed before pulling the trigger, but these changes would be counter productive to the style I aim to produce, and in this case it's far more important to me that I produce a dozen or so interesting images than to hit 100% of the shots I attempt.
*Depending on the direction of light on the subject I may also manually focus
**Of course while I miss about the same rate with both systems the 5D3 is being used in a tougher AF environment (darker lighting coming from less AF-conducive angles). I'd be the first to tell you that in equally tough conditions 35mm beats MF focusing every time.
Two recent examples:
