It's not silly, at least not on the face of it to a complete duffer in nutritional science (me). Intuitively it seems like nutrition is a highly interdependent system of variables. The effect of a food on your body and blood chemistry might be completely different when consumed in combination with other foods.

Or it might not. Testable! Give subjects the same combinations of foods (maybe scaled by body weight) a set time before consuming the test food, and measure blood sugar delta.

In any case, it might be wrong but it's not silly.