Exactly. If a single test becomes important enough, it will be very heavily gamed. Conventional education avoids this somewhat, because there are so many models

Exactly. If a single test becomes important enough, it will be very heavily gamed. Conventional education avoids this somewhat, because there are so many models by which you are measured against, over a very long period of time. This makes conventional education much harder to game. You need a system that encourages people to optimize for maximum problem solving ability, but a formal grading scheme encourages people to optimize for that instead. This is the single biggest problem with online classes and is why online degrees are not considered as highly as in-person ones.