If you look closely, that’s a lever knot, which is non-cinching. And given the fact that that the human neck can actually support about 2x your body weight hanging below (assuming not obese)… this seems like a reasonably useful safety device.
Just because it's non-cinching doesn't mean it can't restrict airflow and circulation. Not to mention the suspension trauma even if somehow there wasn't strangulation or and internal decapitation or c1/c2 fracture or the many many other problems that come with having so important a body part on a mobile joint. I can't imagine it being good if someone passed out in this position.
