What isn't said ...
... is far more interesting.
ElReg is happy to berate the government etc when they go out and spend oodles of cash on some moving target IT system - I'd be extremely surprised if this wasn't a similar situation.
When I worked in "the yard" (as the place is still known locally) I used to describe my job thus :
The Ministry will decide that they need a certain piece of equipment and will write a specification for it - being careful to be as vague as possible so that they can't be 'wrong' in the future.
We look at the spec, and together with what we know about their needs and submarines, will write a detailed spec.
This spec is sent out to tender, and the tenders analysed taking regard of whetehr we believe the potential contractor is capable and whether their cost and timescales are credible.
The Ministry will then order from the cheapest quote ! In the modern days of 'prime contractor' and all that, it's probably the company that orders it now.
The contractor will write their own spec, and this will go back and forth a few times. This process is repeated as things get more and more detailed. Needless to say, when you buy on price, the end price is unlikely to reflect the initial tender - so many individual bits will go up in price, as will the man hours spent sorting out the mess.
Eventually, a box (or multiple boxes) will be delivered to the yard - all painted the same standard colour (which is probably classified so I won't say what !)
If we are VERY lucky, it will do what the Ministry wanted and not what they wrote. But if it doesn't, then the Ministry can use the vagueness of their original spec to re-interpret what they asked for to make it the contractors fault.
If we are VERY VERY lucky, the Ministry haven't totally changed their mind in the meantime !
Changing software during the project is costly. Changing you mind during the build of a submarine is even more so - especially if you then have to redesign the metalwork and rebuild bits of it. I would be incredibly surprised if this hasn't happened.