Not sure the agree with opening paragraph. Having a licence doesn't mean an engineer knows the aircraft back to front etc. That comes from knowledge. A lot of non-licenced engineers have vastly more experience. In a past life in Europe operators use non-licenced engineers to sign a CRS for tasks that they have been trained on and demonstrated proficiency with. They are issued an approval by companys QA department.
Airworthiness of the aircraft wasn't compromised as a licenced engineer has to conduct the training and approve the paperwork prior to the approval being given by the Quality department. It reduced costs as fewer licenced engineers Meant a lot of airlines use a shift of nearly all non-licenced engineers and just a couple of B1 and B2's.
I think the terminology of "Special task" may be a contributing factor.