It is, of course, written from the point of view of the industry. Too wit, that the purpose of the Defence budget is to fund the industry to make new products that it can see abroad.
From that point of view actually having to deliver on time and on cost to the UK services is a bit of a nuisance.
If, however, you assume the role of the Defence budget is to equip the services to fight the wars the government gets us involved in, then it would be far cheaper, on many occasions, to buy off the shelf from a US or other company where the development has been paid for elsewhere.
The trade off between the two is whether you are more interested in keeping jobs in factories and docks in your constituency or prpoperly equipping the armed forces to do the job properly with minimum casualties.
Politicians, of all parties, being what they are, the priority is always the first, not the second.