Similar to a standard neck grab. Which already exists to show how bad ass and or strong the bad guy or good guy happens to be. But to add extra extra emphasis or just to show how extra bad ass the person or thing doing the neck lift happens to be or how strong or big they are their is a cut away for a brief moment showing the legs dangling off the ground.
As seen in Predator there is a slight cut away to show just how big the predator is compared to Dutch.
Terminator 3 when John Connor is lifted up by the neck it cuts away to show his legs clean off the ground.