The original Wing Chun, when compared to modified Wing Chun, reflects the loss of critical information during the dissemination of knowledge as the system was passed down through the generations. Modified Wing Chun does not have the core codes of the original Wing Chun. Without the knowledge of the five lines and 3 reference points you are void of Sup Ming Dim and the practitioner must completely rely upon the centerline approach to combat. Although centerline is a major component of combat it alone cannot create the 3 dimensional aspect required for a complete system.
Wing Chun systems have many variations due to the knowledge and understanding of the Master and the lineage that produced him. As referenced in the previous paragraphs, the Wing Chun system was discovered and developed in the Southern Shaolin Temple as a martial arts system to defeat all other systems or styles using maximum efficiency. After the fall of the Southern Shaolin Temple the Masters were forced to go into hiding to save their lives. This created a diverse environment of training. Those who had the codes and secrets of Wing Chun maintained them in secrecy. However, those who only had partial knowledge or limited training continued with their training and produced many variations of the original system, even some becoming styles.