Some nonsense being written on both sides of this argument. The sub and those on it make no decisions about when to fire or at what, that is a political decision, so the sub departing after firing a few missiles (the numbers quoted are wrong too!) is irrelevant.
However, the RN are not more productive because they can spend more time away under harmony, that would only be true if the RAF didn't complete defence tasks from their home bases (eg QRA, Air Transport and any other of the myriad tasks that they do without leaving the UK).