This was the one where the media reported that because nobody was found in the front seat it must have been the fault of the self-driving feature. The NTSB found that none of the driver-assistance features were activated, and the driver was probably tossed into the backseat from the impact:

Although the driver’s seat was found vacant and the driver was found in the left rear seat, the available evidence suggests that the driver was seated in the driver’s seat at the time of the crash and moved into the rear seat postcrash. Specifically, residential security video showed both the driver and passenger getting into the front seats prior to driving away from the residence. In addition, the EDR data showed active accelerator pedal inputs consistent with driver activity in the 5 seconds prior to the impact with the tree, and that the driver’s seat belt was connected at the time of the crash. Finally, the steering wheel examination conducted by the NTSB Materials Laboratory indicated an impact to the upper left quadrant, consistent with the driver loading the steering wheel during a frontal crash.

The entire journey appears to have lasted less than a minute (9:07pm is mentioned both as the time the car left the driveway, and as the time of the crash), so it's unlikely the driver jumped into the back seat as a stunt while driving.

https://www.ntsb.gov/investigations/AccidentReports/Reports/...