How to prevent one app from saving/restoring any Saved State I want to turn off the restoring of an application window (in my case, iTerm).
How to turn it off, but just for this specific application ?
There is a specific command to prevent any app from saving state, rather than just locking the state folder…

defaults write com.apple.Preview NSQuitAlwaysKeepsWindows -bool false

If you don't want a permanent switch, just to prevent it on one single occasion, then deleting/moving the Saved State folder in ~/Library/Saved Application State/ would be the simplest.