The wing chun guy is chasing his TKD opponent, which can get you into trouble if the TKD opponent kew how to circle like a boxer with his footwork
not the best, but here is a better example starting at 0:44 into this clip
https://www.youtube.com/watch?v=jU8B6eNm2zs
When i close the distance, i can do it in one step and completely shut the opponent down and distroy his body structure to the point where he is off balance and can't move or step away. it's not check, it's check mate, but you have to have very good timing to be able to pull it off.
Starting at 2:29 into this clip
https://www.youtube.com/watch?v=jB3eW0hfy0U was the closest I could find on youtube to the timing I am referring to, except I don't necessarily stand still and wait or step directly down the centerline, I wait for the opponent to come at me, I can bring the fight to the opponent, or I can cut the opponent off by being proactive. The secret is to take the inner gate centerline as Hendrik has mentioned on here before.
In wing chun if you have to chase the opponent in any way, form, or method, you've already lost the wck timing. Regardless of whether you are chasing his hands or chasing his body or feet. You will be at the mercy of the opponent if he is experienced at long fist power generation arts such as CLF MMA or western boxing or close range grappling power generation arts such as wrestling/BJJ and you will always be one step behind on timing reacting and being lead by him instead of being proactive and leading him. The opponent will completely control you timing and distance. In my experience there is no superior art, every art has it's strengths and weaknesses, wck strength is targeting the inner gate centerline and it's weakness is chasing an opponent at long range. Whoever control the distance and timing in a fight can usually play their game and win the fight. Lyoto Machida in UFC is a prime example of this, he has dominated every one of his opponent when his distancing and timing in on point. The only times he has lost is when his opponent was able to control the distance, such as with his fight against shogun Rua.
There is no principle in wck that tells us to ever chase an opponent, this is a modern evolution based on people's interpretation of the art.