Hi, when I create a new game in singleplayer, I choose Insanity as a preset, change The Power and Water Failure Time to 1 week and 5 days respectively and start it, the game seem to overwrite those setting with the preset ones because I don't have them available at the start. I tried to do the same thing with the standard difficulty and it seem to work but I can't say for sure about the duration since I can't check it right away but it work in buildings.
I made those test choosing the regular spawn option in Dannemora.
#Power and water preset setting overwrite
modest spoke
kind otter
Its not just there, there's a lot of the settings that doesnt do anything. I have yet to see the devs speak up about this. You basicly can use the settings, beside a few of them and only when creating a "Standard" game.