Look, the clearly most likely scenario here is that the driver got confused, overrode the AP, and then failed to maintain awareness as they commanded the sudden lane change. Obviously that's not what people want to hear, but it's the best explanation. I've pulled AP out and changed lanes manually, probably rapidly, on a bunch of occasions. All it takes is to do that when not paying attention...
All your logic was equally applicable to the accident in the linked article, and it was all wrong there too. (Also... Musk didn't "blame the driver" in the linked case? Not sure what you're citing. Tesla generally doesn't say anything about their customers' accidents, for some very obvious reasons.)
Just wait. All I'm telling you is that I drive with this product every day and I'm not seeing FSD behavior in that video. If it turns out I'm wrong then I'll sheepishly admit it. But I know which direction the spin runs and my BS detector is pretty good.