It seems to me that if the requirement is for an assessment as part of the AOW class then it should be part of the class, and I'd expect the whole class to follow a structured method from start to finish. The instructor's plan for how to provide any remedial training that's necessary or deal with a student who isn't ready to continue is a separate issue. Simply insisting on a refresher "course" before assessing the skills strikes me as a failure to offer a fair option.
That's how I see it.
AOW requires five dives, two required and three at the student's choice. The navigation dive usually takes the whole dive to complete the required skills--in fact, I recently had two students, and it took me two dives to complete all the skills at the depth we were working. With the other dives, however, a much lesser portion of the dive is spent on the required skills. If a student selects an option like altitude diver, in fact, no part of the dive is spent on skills. When I have a new AOW student, I always choose one of the dives with the least risk and the least amount of required skills for the first dive. That gives me plenty of time to assess the student's needs and even work on them--especially buoyancy and trim--throughout the dive. The rest of the dives go the same way. I can spend part of every dive (except navigation) working on whatever I want to work on with the student.
I can even add in extra stuff. For example, the pair of AOW students mentioned above completed their deep dive during a drift dive in south Florida. We had gone over pretty much all the knowledge reviews for all the dives in the book, not just the five we were doing, before that. The boat dropped us off on the deep side of the reef so that we could get our needed depth and then headed to the shallow side to drop off the rest of the divers. We went to depth and did the few required skills, and then I had them navigate to the shallow side to complete the dive, with the two taking turns holding the dive flag line and leading our direction by compass. They only got credit for the deep dive and still had to do four more, but on that dive they did everything required for the boat dive and drift dive, too. Throughout the dive we identified fish enough to get credit for that one, too. They had to use their compasses to get to the shallow side, so there was navigation practice. The dive plan also fit into multi-level/computer. Of course, as they went over the reef, buoyancy control was important.
If I have a student who looks pretty bad on that first dive, I assure you that student will be a different diver after five such dives.