the average fresh from the flight test CPL does, in general, not have a high enough level of flying skill to properly demonstrate any manoever
I would agree with this observation. Usually, a PPL holder with 300 hours is far more suited to a FI Course than a freshly minted CPL holder. Hour building (wasting) is no substitute for real experience gained by a PPL who is not set on meeting an hours target.
How many car drivers, lorry drivers or motorcycle riders pass their test and rush off to become instructors?