I see what you're saying, and I see what appears to be smoke plooms coming off the rear tire twice, (which indicates good braking by the rider, not leaving it locked up but trying to maintain threshold braking) but I'm not entirely sure we're seeing it correctly. If however, he did lock up his rear tire twice, the driver behind him is still way late on reacting to the braking going on in front of him. Watch the nose of the car...it doesn't dive till waaaay late. That's when the car driver gets on the brakes.
Now you and I know that bikes use half the distance to stop that a car uses from the same speed, so that car driver has to be paying attention when a bike's in front of him.....and he was not.