Since all ILS approaches are flown with dual autopilots
I might be missing something here - but I thought the only time you are supposed to engage dual autopilots for an ILS is if the intention is to conduct an autoland (737) . And one important reason for dual autopilot is for the automatic go-around facility which may happen so close to the runway that the wheels may touch and that it is well nigh impossible for the human pilot to break visual at runway level and then not only decide he is not well placed but also to hand fly after barely a second of visual segment.
On the other hand a single autopilot ILS can be flown within the same flight path accuracy as a dual autopilot ILS to the minimum disconnect height of 50 ft and if not visual the autopilot is disconnected and a manual GA conducted. There is simply no point to making a dual autopilot approach just because a GA may be needed. So what? A competent pilot should have already been certified to conduct manually flown go-arounds both all engines and one engine inoperative. The danger is disconnecting the dual autopilots below 400 ft when landing is assured and then being caught by the significant mis-trim which was automatically applied on dual autopilot at 400 ft.