Boxing shows us there are certain areas, such as the temple and jaw (the 'Sweet Spot'), that are more likely than others to cause sudden loss of consciousness when hit.
And yes, there have been a number of knockouts or near-knockouts in boxing as a result of a hard looping punch that lands near the back of the neck or behind the ear (Danny Garcia vs Amir Khan, 2012).
However, a knockout blow to the side of the neck and with a karate chop (that's probably not what it's called) is something a bit different.
That's a move many are not familiar with.
It must take years to learn how to do this. Also, it probably helps if your target is stationary?
Could a female, obviously one who is advanced in this specialty, ward off a much larger male attacker this way?
Even if you're just "messing around" like the guys in the video, never engage in these types of exercises, including boxing sparring, unless someone who knows how to give proper aid to a person who has been knocked out is present (and obviously she/he can't be the person who was knocked out).