Hey RC_Fanitic,
I haven't quit thinking about this one. I didn't think about it at all when I watched the video. But after you asked, I realized that it might be something different. I'm still thinking.
Consider this. Two rotors going one direction, two going the other. All of them variable pitch instead of variable speed.
If you increase the pitch on the two clockwise rotors and decrease the pitch on the counterclockwise rotors so that the total lift stays constant, what happens?
When I go through these kind of mental puzzles I tend to think to extremes. So increase the clockwise rotors to an extreme pitch and the counterclockwise rotors to zero pitch. Those counterclockwise rotors aren't doing much of anything. No lift, not much drag, just hanging out. The two high pitched rotors are doing all the work. But there's another force they are creating. At high pitch and at opposite corners of the aircraft, the clockwise rotors are each creating forcers other than the downward push of their rotors. Since outer tips of both blades are moving in the clockwise direction with relation to the entire aircraft and they are farther out than the inner tips, they have a longer moment arm. They'll act like paddles and push the airframe in the counterclockwise direction.
Again, I'm no expert. I'm only a physics fan (physics phan?) and an engineer who enjoys thinking out how to build things.
There it is, that's my guess. Increase the pitch on two rotors, decrease on the other two rotors and the outer end rotor drag overcomes the inner end rotor drag, yawing the entire airframe.
Just a guess. But nobody else was bold enough to posit an opinion on how it worked.
Dave