Well DFC the subject of engineers holding approvals who had failed the licence was the subject of a crewroom conversation only a couple of days ago. A number of us remember it well and could name names if necessary
Approvals were dished out on the basis that X was a good egg. There were no formal examinations of any kind.
This was why the CAA changed the system to make it a requirement to hold a basic licence.
You appear to have a British Airways hat on with talk of apprenticeships. None of the engineers in question had been trained by the operator they were all "imports".