Over the years, I have heard philosophers note that "P is an empirical question" with the implication that we should withold judgment on P. But, the observation that P is an empirical question should lead us to suspend judgment only if P is an open empirical question, one that current empirical work indicates is not largely settled.
So, for example, I take it that it is an empirical question whether or not there are elephants in Africa, but it is not an open empirical question. Similarly, I take it that it is an empirical question whether or not surfaces often constitute affordances, but the point of my arguments about exploding boxes is that it many cases it is not an open empirical question. They are empirical questions where our scientific understanding is far enough along that we know that the pick-up-ability of a thing is not often constituted by the surfaces of a thing, but also by its internal structure. Similarly, it's an empirical question whether a particular pattern in an electrical field specifies something edible, but it is not an open question whether a particular pattern in an electrical field specifies something edible. It does not, as we can tell from, for example, the experiments Kalmijn did on sharks.
In cases of empirical questions, let's just cut to the heart of the matter and see whether the empirical question is open or not. That's what's typically up for grabs regarding a claim; not its status as empirical or a priori.