Problematic and completely unexpected. No one speeding past you is going to brake check you for moving into their lane, so this kind of behavior from a computer is inevitably going to lead to accidents.

You can’t know what is in front of the other car or why the Tesla braked. It could have been passing a slower car or truck (likely given the situation as described). If that car swerved a bit into the Tesla’s lane, braking could have been the right choice.

The car behind is always responsible for maintaining distance.

Realistically, if the tesla felt squeezed by a car it was passing, going a bit onto the shoulder would have been what I would have expected from a human driver. But no auto steering, tesla or otherwise, is going to do that.

> of course, in a large sense, the one that hits from behind is at fault

I don't know where you live, but where I live (Denmark) brake-checking is a serious traffic offense which can lead to loss of license. While the driver behind has to keep distance, you cannot brake for non-traffic reasons. I.e. you cannot simply brake-check someone on the freeway because you think the driver behind you is driving too close (also a serious offense).