Lots of words for a simple activity, we have procedures to ensure we to not spread contamination at our nuclear power plant, and our workers need to practice good behaviors to ensure this is met. We have a similar activity for industrial safety.
The DLA is basically a series of tasks that need to be performed, and if they are not performed to requirements, you loose points. There are "circuit breakers" that if you get the activity wrong, you fail.
Being an evaluator is just a step above having to fire someone. As an evaluator, if they do not perform the circuit breaker activities properly, then you must fail them, and they need to re-perform the entire activity. If they fail again, then they need to go to their management for determination of the next steps (i.e., this is a performance issue).
Today, someone that I used to work with, missed a critical step. It was a terrible feeling, having to tell him that he "failed" the evaluation. He took it well, stayed around, and he re-mediated successfully.
There are four evaluators per week, with three classes per day (12 students per day). Today, we failed five on the first attempt, but luckily they all passed the remediation. Only four more days, I hope our success rate increases, because I do not like having to "fail" folks.
It makes for a long day, multiple sessions of watching people perform these activities. It is physically, and sometimes, emotionally taxing. Sounds a lot like every day life!