ADF clarification

[Steel God]

The optional rules are set at the start and can't be changed afterwards but the auto defensive fire settings can be changed(A/I menu).

I understand the the phased play but was curious why it is possible to change the auto defensive fire settings during a match.

I have never seen or noticed that.  Well assuming that is "working as designed" I imagine the only change during phased play by turning off ADF would be the need to manually defensive fire, which would require a save and an email to your opponent mid-turn.  That would double the amount of email exchanges per game.  I always use ADF with phased play which is why I guess I never noticed it could be switched on and off (because I impatiently wait for turns now, can't imagine doubly that penance)