I dont know my brain might be faking whole problem.
Sometimes it feels like I start pressing button again because it didint go black.

I think same as HtheB that power menu activates some double press options and it waits that default 500ms.
Tried changing double press delay to 1ms but it didint help.
Do I need to reboot after I apply it? Didint try that yet.

Edit: Double press is enabled but doesnt do anything. You can test it just by double pressing.
Edit2: Double press is not enablet on lockscreen. Screen goes black and opens again if you try it.