We already know that humans are human-level intelligent, so we don't need to devise a test to prove that they are. If AI >= highest level of human intelligence

We already know that humans are human-level intelligent, so we don't need to devise a test to prove that they are. If AI >= highest level of human intelligence, then AI > human intelligence. It is less accurate because it will miss any AI that achieves a precisely human level of intelligence, but it is probably also an easier test to define than others. Of course simply increasing the scale of the model does not count as an improvement, there is nothing novel in that suggestion. But you are right that it opens a can of worms as to what an improvement is. Does an improvement count if it improves the model in the 80% of scenarios that only appear 20% of the time, while similarly reducing its performance in the 20% of scenarios that appear 80% of the time?