Well, you would think it would do something rather than just giving up telling the driver "you got this, right?". Even continuing to follow the right or left lines (whichever it still senses) would avoid the barrier. A minimum default might be to let off the gas and apply brakes if the driver doesn't take control. That would get someone's attention if the other alerts did not.
Go back and watch that recreation video again, especially from :27 to :35. Your suggestion that I bolded is exactly what the car did. It lost the right hand line because the lane widened out of it's spec and the right hand line was dashed and faint. It locked on the left hand lane line and tried to keep the car in the lane. When the highway split, what
should have been a triangle with hashmarks up to the barrel was actually one nice bright line, and some faint hashmarks. The left lane line of the lane he was trying to be in doesn't exist. So the car followed the one lane line it could see which, due to IL DOT negligence, ended up becoming the right hand line of the diverging lane. The car followed that line right into the barrier. Perhaps if the lane lines had actually existed, the Tesla could have followed them.
If you freeze it at :29 you can pretty clearly see the car locked onto the left hand line, which is diverging from the highway, and will hit the barrier. You can also see that the left hand line of the lane that he was trying to be in doesn't exist. You can't track something that doesn't exist.