Really? Most scientific evidence shows that the constricting of the snake literally stops the flow of blood, making the animal pass out quickly.
When executed perfectly, a head lock has the potential of knocking you out within seconds. Your putting pressure on your jugulars, not the throat. This stops blood flow to your brain and can make you pass out under a minute. You'll also feel the effects immediately.
Snakes have had million of years to knock out their prey efficiently and quickly. The longer a prey item is struggling and scratching, the more damage a snake is going to take. Snakes have evolved into very effective and efficient killing machines with the power of their constriction.
So yes, whacking is very inhumane compared to live feeding, so is stunning. The chance for error is high, and if it takes more than one whack, you did it wrong.