Incorrect. On most devices after the power is cycled you can’t use the camera on the lockscreen. You have to enter the password once before that feature is enabled. And if you’re doing a screen replacement you need to power it off or you risk frying the backlight. How many cellphones have you repaired? 1? Hundreds? Thousands? It was my job for years, and my point is just don’t assume things are simple.
You almost always need to the password to test a phone thoroughly. You can see that the screen works on the lock screen, but what about the front facing camera, and secondary microphone that are attached to the screen and need to be transferred, or replaced if you do it like Apple. On newer iPhones the slightest defect can cause face id to not work. On laptops it depends. Sometimes live USBs don’t have the right drivers to test all the hardware. When you assume things are simple you’re usually wrong.
Letters of the alphabet, ACAB