Only one way to find out. Find someone who trains this system to spar using this technique against a round house. I personally don't think there's any need because be cause in the video itself, it shows what happens when you miss. Even the teacher that the teacher realizes this which is why he changes the target from the shin to the knee.Do find it amusing when practitioners of "long arm" styles try to explain it to those who haven't practiced it, yet don’t apply the same logic when discussing "mantis" asking question's of something not practiced.
The picture below is the truth even if you are super fast. If you miss the kick still goes through and you pay the price.
But you are right. I'm don't know what I'm talking about because I don't train Mantis. But I wasn't the only one who saw something wrong with that punch knee / punch shin application. Even the teacher changed it up.