5 points
I have never heard of that feature. If I turn my phone off before going to bed, it’s because I want it to not ring the alarm at the usual time. Telling it to turn off makes it do a complete shutdown. What you’re describing would require some sort of hibernate mode.
2 points
it’s not like hybernate on a PC. it’s more like the circuits in the phone (probably the BIOS) still have the clock running when off and know the time when to boot into that special mode. my newer phone even has a checkbox “keep alarm active” on that shutdown screen where you confirm the shutdown.
