Afterthoughts on Mittell’s decentering of text in genre categorization

This might be a very minor part that I find somewhat contradicts Mittell’s constant decentering of text in genre categorization. In the second paragraph on page 10, he says, “Even though genres do not emerge from core textual essences or structure, the use of generic categories is predicated on a cultural assumption that genres do in fact refer to internal textual features.” To put it in another way, a wide cultural use of genres are premised on textual attributes, “even though genres are not dependent on textual properties.” Then he goes on to use the example of “NBC show” to substantiate the point that a term not suggestive of generic texts but of industrial origins cannot gain a wide circulation. But to some point, I don’t think it is a good idea to deny any possibility for more arbitrary industrial or critical decisions to become the core textual structure (if there really is something as a “core”)  theoretically. Otherwise, the text itself is again elevated to a more superior position than discourse in other dimensions, which I feel is not poststructuralist enough.