All punching power should come from the body and not just come from the shoulder. This is why when a boxer looks at a WC clip, he won't believe that "shoulder only punch" can generate enough knock down power.
In this clip, you can see
- body movement,
- waist rotation, and
- legs spring.
In this clip, you don't see much body movement at all. I do think Ip Men's WC system training method has some issues. It makes beginners to forget about the body and only think about arm.
The issue is after you have developed this bad habit (only think about arm movement and not think about body movement), it's very difficult to remove it later on.
To keep it simple in the beginning training stage may be a good idea. But the important concept (such as body push/pull arm) should be addressed during SLT training stage.
The day that you can punch without using your arm, you will understand "power generation" better. Should you start this during SLT training? I think you should.