Like the man in the video said, just nerves, the pig was dead after that up close shot.
The close up shot was a body, not a brain shot, from the appearance of it.
Reflex does occur after brain death, but even a human head is conscious, can hear, and respond with eye blinks for at least 15 seconds after severance from the body.
For that reason, I prefer to use a brain shot on my hunts.