It seems they don't test for that, since they use the second-best human solution as a baseline.

And that's the right way to go. When computers were about to become superhuman at chess, few people cared that it could beat random people for many years prior to that. They cared when Kasparov was dethroned.

Remember, the point here is marketing as well as science. And the results speak for themselves. After all, you remember Deep Blue, and not the many runners-up that tried. The only reason you remember is because it beat Kasparov.