You certainly wouldn't save gas by switching it on. It's a comfort setting
Did you really just ask that??
I guess that's why they shouldn't let amateurs comment on gas appliances
What provision was made for any incidents of the flap sticking in the ( partially ) shut position when the boiler was commanded to fire up ? As I understand it there is no differential air presure switch monitoring air flow into the combustion chamber. How would the control system know that there was inadequate air flow for completer combustion ?
Did you really just ask that??
I guess that's why they shouldn't let amateurs comment on gas appliances