I've read that thread, but I think it's a little different. Night light is turn ON automatically without problem but turn off is problematic.
I use dark mode, but I believe it has nothing to do with night light.
a) settings -> display -> night light -> schedule : turns on at custom time
then change start time to 20:03 and end time to 6:44
As I said, turn on at 20:03 happen but at morning at 7:00 I still see night light is on, but interesting "switch in TOP bar" is off. I have to click it to activate night light and then again to deactivate it.
b) settings -> display -> night light -> schedule : turns on from sunset to sunrise
of course I did switch location on and enable persmissions, to be sure it will work I did leave location on during night.
at the morning same problem. night light is still activated but "switch in TOP bar" is off.
if phone is unlock ( I am using it or just watching on calculator :-) ) then night light is turn off without problem.