They edit their videos to remove the mistakes. It's all a lie if it only works 90% of the time and you don't know when it's going to fail after being lulled into inattention.
Waymo made a very good point about this, fundamentally that's the problem with a progressive rollout - drivers will stop paying attention when the software is "good enough", and the result will probably be crashes. So for them, it was all or nothing - either it fully drives itself, or it's not worth deploying.