That's what you get with placemen pollies. they don't understand their briefing notes.
I suspect what he meant was interval between deliveries, as opposed to total production time. It is clearly madness to suggest that - particularly the way BAES operates - one could build a boat in 18 months. On the other hand, it is also madness to continue building boats such that it takes twelve years between cutting steel and going on sea trials.
It won't be easy, but it has to be done. Ir also means the arguments about build capacity vs number of boats will need revisiting.