Sorry Bruise, it can be slow to show.
Loki, the attack to the throat was evaded by slight movement (Dick stepped to the left and forward in the very beginning, watch carefully...) and the attacking arm was pinned to his body with his left arm.
When you pin someone's hand or weapon to your own body, they can't do anything with it. It's the safest place to be.
It is hard to see from the video, but the attacker, after Dick moves into position, is hardly able to even SEE Mr. Severance.
His body has been turned away by Dick taking his arm.
Can you see that ? The opponent has been controlled, turned out and away and dispatched, all with one arm.
No, he didnt cut thru the breastbone. Just cutting the skin is enough.
He might not need to cut at all, just use the chest as a guide to other places.
The stab wasnt into the chin, it was into the throat, which is a fast kill.
The trick here is to watch the feet as much as anything else. Dick could be using a ballpoint pen or a really sharp piece of gum.
Watch his body movement from the beginning. He isnt just standing there like a statue, waiting for the attack and trying to deal with the attack by using his arms and his knife.
He is moving his body, from the beginning, to keep himself out of harms way and to put his opponent into a vulnerable, controllable position.
Have another look and pay attention to Dicks' legs.
This isnt kali, but there may be some similarities. Please relax and take what you like and discard the rest. It's just a few ideas to consider anyway.