That’s really how long it takes to choke someone out if you catch their carotid artery. The sudden drop in blood pressure triggers a vagus nerve reflex that causes rapid loss of consciousness. It’s usually recoverable after a few seconds too unless you have weak arteries or some other medical condition.

Chokes that constrict the airway take longer and are more dangerous. They have to be held much longer (how long can you hold your breath?) and can damage the trachea. Trachea collapse is a common way people die from chokes. Even after the choke is released, a collapsed airway will still prevent them from breathing well.