If you know what you are doing you can cut the breathing and also cut the blood flow and you go out...but if the guy can breath through 20 percent of his windpipe, and only one of the arteries is cut, then it is slow...and if the guy is struggling, he will use more oxygen, but he is still partially sucking in some air.
20-30 seconds is pretty long. Freak accident, sucks.
Might have been better if the kid knew exactly what he was doing...actually...guaranteed it would have been a different outcome if this kid had choked someone out before and knew what it felt like...and was doing it properly...safely.
Maybe it's a case of when the bullied fights back....gonna suck for that kid....better get ready for a life of psychiatrists or a lifetime in and out of prison....hopefully he can get over it. Gonna fuck his family up too. Sucks...shitty story.