We believed that chess and go proficiency were good proxies for true AI. They weren't. They were proxies for advancement, but the underlying issue is that we don't know how much we don't know about the human mind.
Every AI advancement helps us learn more about our minds, but the amount we don't know is still unknown.
The moving of the goalposts was not done because "we saw the code" it was because Deep Blue and Alpha Go were obviously not AI. Again, we were just wrong about those tasks being good proxies.