I'm no engineer, but it would seem to me that MOD had the same choice that every car owner has to make. You can get it serviced to the manufacturer's specification at a properly accredited garage using propriety parts, or insist they do it in a different and quicker manner which will save on labour and get it back by tea time, or you can go to a bloke on the industrial estate who will do it cheaper still, using "generic" parts and get paid in cash. Which of these three options for the K ESF fit was chosen is a moot point, but I have a high incidence of suspicion that it was not the first!