Right. I'm pretty sure this was the video that triggered the change (it was widely reported and viewed):
https://www.youtube.com/watch?v=MrwxEX8qOxA
Hmmm, this video may be demonstrating the "use case" (or whatever term Elon used in his tweet) to describe that one last issue -- sun's glare over the crest of a hill, on a curve.
The safety concern with this video was not the Autopilot's error, it was the driver using his hands to record video. This is illegal in Ontario, Canada as you cannot use handheld devices while driving. Shame on this person.
Autopilot is not perfect and most likely will not maintain a perfect accident-free record, with or without restrictions applied. Safety needs to always be top priority, and while it's not a perfect driver I'm 100% certain that Autopilot pays more attention to road conditions than I alone ever could.
And just like me, it's not perfect but so far there are probably 2000 km of Autopilot driving under my MS's belt(line), so I'm not speculating here. I've thoroughly tested the system under pretty much every sort of condition.
When the 2 of us are paying attention, it's been always safer so far. Any wild actions from AP -- and there have been a few -- play out similar to a driver spilling a drink or accidentally jerking the wheel. Accidents happen every day with human pilots.
I've lost friends to head-on collisions before AP was even possible.
So ya, Elon suggests true autonomous driving will need to prove itself several times safer than human drivers, but I suggest that having both available whenever possible is better, and that includes the many 2 and 4 lane highways I regularly traverse that don't have a median / barrier.