Hi Keith,
Hopefully you’re not mistaking this ‘system’ with anything modern, or worst - something that will give you an ultimate answer…
These “sytems” seems to be made as a remedy for obsolete company image and shrinking amount of Jag technicians with skills (“…hey, Japs have managed to change something since 70s”) Step-by-step problem generator. Like playing classic card RPG for employees which are not yet up to a certain level or advanced employees not having time to look through all the issues /play the RPG with mentioned earlier. The amount of “additional” offset and black-box-interfaces with rat nests inside will be your guide…British version of Epipen to all your problems.
Have a look here: