First, that there is an implicit assumption about how cognition and consciousness are defined, but there is no real definition.
Following the example, it's not defined what a duck is, and "philosophers" actually don't try to elevate the question - they try to find answers to it.
While a "strong" test for example would look appealing, the problem is that there is no real model of weakness/strenght, and while a human would pass all the possible models of humanity, a computer would surely pass only the ones it's programmed for.
Another thing is that in order for a computer to truly mimic a human, that is, to fool people for 20 years about movies/music/sports/family/relationships, but also other abstract experiences, the computer would need to experience them, and especially, elaborate them in a human way.
Which is again, very "open", and it's the core problem.
Even excluding the openness problem, the Turing test in the way it's posed, looks to me as the photorealism problem. You can achieve it in a static picture, but once you freely move in a 3D world, you see the flaws that show that what you're experiencing in reality is a limited set of limited algorithms, which are used to workaround hard problems (workaround is the key).
I think exactly the same arguments stand, that is, in order to mimic a human in such a high level of faithfulness, very hard problems would need to be solved, not just worked around.