"If an examiner can't determine that in 30 minutes of questions and two hours of flying, the examiner has learned nothing about assessment."
I totally agree, however to gain a Part 142 OC the applicant needs to demonstrate compliance with CASRs, MOS and FE handbook. Additionally Flight Examiners will be subject to surveilance when conducting flight tests by CASA standards people to make sure they are assessing every unit of competency in MOS 5 and conducting the exercise IAW the FE handbook. An administrative nightmare with no safety related evidence to drive the change - it's all about aligning with someone's take on ICAO flight crew licencing standards. The FAA list the units of competency and leave it to the judgement of the FE as to how many he needs to observe to assess the candidate's performance.