Very true, for beginners that have no fighting expereince, they must start with constant punching to get the muscles properly align and develop force and energy control. Augment this, with push ups.
Punching in ngo cho kun is done with the arm staying close to the body and during the release the forearm twist with the fist acting like an arrow head goes for the target.
Just like any blunt instrument the principle to penetrate a wall is to have a twisting effect an arrow, a bullet or a drill bit is a good example and this is what ngo cho kun punching technique is about.
The first two big knuckles must line up with the wrist and with a jerking motion the fist twist into the target. The legs, the hips and the shoulder must provide the main push for the fist to penetrate the target not the arm, and then tensing at the last minute the strike, to give it a solid impact the twisting will give it a penetrating blow.