I'm not familiar with the boolean circuit problem, but I wonder if it's an instance where the NP hardness comes from specific edge cases, and whether your experiment tested said edge cases. Compare with the fact that the C++ compiler is Turing complete: its Turing completeness arises from compiling extremely contrived bizzarro code that would never come up in practice. So for everyday code, humans can answer the question, "Will the C++ compiler enter an infinite loop when it tries to compile this code?", quite easily, just by answering "No." every time. That doesn't mean humans can solve the halting problem, though.
But, the bigger point is why are not others doing this kind of research? It does not seem out of the realm of conceptual possibility, since someone as myself came up with a test. And the question is prior to all the big AI projects we currently have going on.