One of the things Tony Blauer states is that “everyone flinches”. What about a professional boxer? They are used to fighting, being punched in the face, would even a professional boxer flinch? When startled they flinch:
You’ll noticed the first flinch happens at 4:20 into the video. Muhammad Ali flinched off what he was saying, not off anything Freddie Starr did to him. Then at 4:45 Starr makes a move with his fingers towards Ali’s face and Ali does a beautiful demonstration of a startle-flinch response.
As for Starr, even though he was doing this all as a joke, showed how a predator will lure you in, get you comfortable, and then spring the trap.
Make sure your self-defense training covers these ambush moments and how to convert the startle-flinch response into a tactical action.