You know in a video game or a movie, how the hero easily grabs a knife from an attacker and subdues that enemy? Well, that's in video games or movies — fantasy! Real life is different.
However, as numerous YouTube commenters pointed out, the "real life" versions of the attacks are missing the confrontation. They simply show the attack, which seems to be the point…to make this point.
Want to know how to protect yourself if someone pulls a knife? Run and scream for help. Someone should make a game about that.