Alternatively, another way to turn off a phone running Android 12 would be to hold the power button and the Volume Up button. Which would mean a lot of accidental screenshots in the process.
9to5Google reports that this assistant feature was found in the code of a beta version of the Google Search app. Though the power and volume up combo for turning off the phone doesn’t work yet. At least as of Android 12 Beta 1.
On one hand, it’s probably not a feature of the Google Assistant that most people will use. After all there’s no reason to turn off your phone under normal use case scenarios. Unless if you do so with relative frequency, then the process of doing so will be a little longer.