I am pretty certain that with the wonders of, hindsight and sow motion video, etc then in this particular situation we can reasonably safely say the driver was not in a huge amount of danger.
HOWEVER
Would Mr jack be happy to sit in a car without a halo, while several other cars are fired from air cannons at his car at similar angles and trajectories ?
Personally i would never do so, but in a car with a halo I would.
This one time the halo may not have genuinely saved the drivers life, but sooner or later there will be ONE occasion when it does save a drivers life, and that ONE time will be complete and utter total validation for having halo's on every car.
That is the whole point of any safety device, the one in ten, or one in a hundred, or the the one in a million where the device does save a life.
Personally I hated the look and design of the longer F1 cars once the ruling came out that drivers feet have to be behind the front axle line, I thought the short compact cars looked great, but they were not safe, and even minor crashes resulted in broken legs, feet, ankles etc, so I totally get whey the cars are now longer, they are so much safer, still does not mean they look any better, but I just have to get used to it.