I don't get this. You are willing to play around with flags, when there is no reason to do this.
With V8, I guess there was, since it usually takes 30s or so for your pause to be written into the config. But with V8 issues doesn't exist anymore. You click pause, and reboot the system. Pause will be saved instantaneously with V8.
You are welcome to raise a ticket in V8 GitHub for dev to add an option within the fahclient to tick where it would pause upon restart regardless of you paused or didn't before reboot.