If you’re a long-time Android user, you’re used to long-pressing the power button to (logically) power your phone on or off. For a while, long-pressing the button while the phone was on also enabled you to restart it, lock it down, or signal an emergency. (For a short time during Android 10, you could also use it to take screenshots.)
So you may have been a little perturbed if, after you upgraded your phone to Android 12, you found that long-pressing the power button did not bring up the shut-down menu but instead activated Google Assistant. This is something that was instituted with the new version of the OS, and it’s supposed to be A Good Thing.