David,
I agree this wouldn't stop the 'Nil Points' but it would stop the guns firing when getting up & moving between lanes which I have seen on more than one occasion when the gun is left switched on. Personally I wouldn't use a fixed single shot feature as I would get sick of turning the gun off & on between the two targets on a lane, if you had the option you can always set it to one if you prefer & if you did get 'Nil Point' on the '2' setting you've only yourself to blame.
Pete.