We are taught the following in driver’s education:

If a car’s power fails (accidentally, or on purpose by turning the key to OFF), even if you have power steering and power brakes, these systems are still supposed to work–BUT, you have to use more muscle.

If I had any sort of modern fly-by-wire car, I’d sure get over to an empty lot and try turning the key to off and verifying that all systems are go. This approach would good practice in case of an acceleration problem, as with Toyotas, and for verifying that things still work, even without power, would provide comfort and some important practice.