Dedicated to Using Gluten-Free Brands?

If you have a G-F menu, did the consultant or who ever designed it specify certain brand names for various items such as Vinegar, Rice, Pepperoni, Sauces etc. to use regardless of cost or convenience? Are Buyer & Chef aware of these requirements and either committed or required to use these brands? (Why: Because certain brands of various ingredients are Gluten-Free and Certain brands are not.)