It is quick and turns the body so that a center line attach becomes a glancing blow if it connects at all.
In my Jujitsu training we would traverse the length of the dojo using Chinese Hidden Foot both passing the leg behind and in front. Facing the Shomen through out, moving down to the right and back to the left. Keep the knees bent and the head below the imaginary ceiling fans five feet off the mat. Another cool drill is to move down the line switching from hidden foot to horse stance (by turn 180° on the balls of the feet.)