is the following examples is the key.
Black gets the 3 white stones in a snapback
If would protect against the snapback, Black would cut white in two killing more white stones.
Because White can just capture the cutting stones then.
A variation of path 2
billyswong: However, in path 2 and 3, white results with loss of more than the original 3 stones with no gain. But the snapback in path 1 can be used as a ko threat later on.