He's not. Did you read the first technique to cut off HV? Turn off the key. No, firefighters don't do that in ordinary vehicle crashes already, yeppers, a special complicated technique for those newfangled hibrrids...
As stated previously, the best method is to turn the ignition switch off. This simple action:
Turns off the engine and the motor, which prevents electric current from flowing into the cables from the motor or high-voltage battery, and,
Turns off power to the airbags and the seatbelt pre-tensioners.
After turning off the ignition switch, it is recommended that emergency responders remove the key so the car cannot be inadvertently restarted. To let everyone at the crash scene see that the key is removed, place it on top of the dash, directly in front of the steering column. In this location, it can be viewed from every side of the vehicle.
After discussing isolating the 12 volt battery, also a special and unique technique (/sarcasm) to those hybrids...
With the ignition key turned off and removed and the 12-volt battery disconnected, the hybrid vehicle is safe to work on for vehicle rescue evolutions. High-voltage electricity still exists, but it is isolated to the battery pack in the trunk.
Unless one's got passengers in the trunk, the extrication then proceeds normally.