I've watched the videos (and yes, they are horrible, and no I won't post links to them here), and for whatever reason, the people in them have faked it.
How do I know? I've killed a lot of sheep using this method. I know what happens. I know how much blood there is, and the noises that are made, and how they don't just lie there limp. And, in the latest one, while they're reading out the rant, the guy does not move. Not even the slight movement that would show he was breathing.
I don't condone anything about what these people are doing. I don't condone propaganda. Taking life is wrong no matter what dogma you live by. But, I do wonder, why are they faking these videos?