Recently in High Sierra I have seen a change how Apple is handling the defaults. To be specific System Preferences > Security & Privacy > General tab > Require Password option.
Previously till macOS Sierra, we could change the values using defaults command in terminal, like:
defaults write com.apple.screensaver askForPasswordDelay -int 1800
But High Sierra is not saving those values in com.apple.screensaver plist anymore. I have tried tracking the file read write activity while changing the value in the system preferences. But I could not track it down. I need a solution to change the values from terminal. I understand Apple script would be a way to handle this(i would not trust it and it is my last option). Any way to handle this in HighSierra using terminal would be a great help.