I see multiple means of expression as providing the option of writing a test or doing an oral exam or showing competence on the job. Some people don't do well on written tests. However, in all cases, the performance standard would be the same. My experience with critical skills (like chemical hazards) is that any drill & practice or tests should replicate the actual work conditions as much as possible.

Thanks for the reference to the other models, Clark, which I'll have to review.