It's basic speculation. SN shuts your body down slowly by not allowing oxygen into your tissues. I didn't say I'm afraid of being either unconscious or dead. Being unconscious is not much different from being dead. What I'm afraid of is being conscious and alert in a body that no longer responds. Watch the case with the chinese girl, for example. In a certain moment, it's very clear that she's still conscious, trying hard to move her arm to clean her face and not being able to. That must feel like hell. A gun or a rope would do a much faster job.
I don't know the proper terms, words for this. There are different levels of conciousness. Somebody can be moving and still be in a state not much different from dead.
I've been heavily drunk, heavily drugged before and I wouldn't mind or remember being shot, killed in such state. It's hard to describe and from a bystander perspective it would look painful, my body would react as expected. But such state is not much different from dead either.
Of course if you survive that you would feel the consequences eventually.
I feel incredibly "lucky" to have experienced that first handed, because it changed the way I look at this kind of stuff.
Of course, it is possible to be fully concious and in incredible pain when paralysed and that sounds terryfing. But it's impissible to tell that just by looking at somebody, like in the case you mention.