What Chomsky is saying is that the control variables don't exist until you create them because the most telling things don't happen until you have a specific hypothesis and make them happen to test the hypothesis.
I disagree. What he is saying is that there is a special rule for languages that he doesn't think you would get at without an enormous amount of data. So a passive learning algorithm wouldn't uncover this structure in a reasonable amount of time or data (I guess it is poor sample efficiency he is worried about). A learning algorithm that has a distribution over it's own internal model of language would be able to ask questions that minimize the uncertainty of the model.