As above, no doubt if the No4 wheel was the only one in contact with the runway then the BSCU would note a discrepancy between the Tacho on the individual wheels. As the other 3 would be similar the no 4 reading would be deemed unreliable and the 'Brake Released' which would have the knock on effect of the Autobrake becoming U/S.
I am not sure if the blog is correct though, for the ground spoilers to deploy it requires both main landing gear to be on the runway and the thrust levers to be in the idle position. You NEED the spoilers to deploy to activate the Autobrake. So the blog doesn't quite ring true when it says the Autobrake activated slightly before the spoilers deployed. The other wheels must of been off the ground for a considerable amount of time for this to be an issue.
I have had the Brake Released ECAM once, I was stationery on stand, released the park brake for push back and got a 'Brake Released' ECAM on the No 3 Wheel. Turned out to be a faulty TACHO on that wheel.