I'm not too surprised by that Phil. It's just another case of same word, different usage in the Indian culinary application. Chaat (chat) is a general term for finger food. While Chaat Masala can be and is used in the preparation of some Chaat dishes, it is also widely used as an additional condiment type sprinkle to spice chaat foods up afterwards. Garam Masala has both of these uses as well. Ingredient spice or condiment.
I doubt that Chaat Masala is necessarily used in the preparation of all Chaat dishes but it is available for addition to taste. Think of plain salt or chicken salt on your potato chips. Chaat Masala is also a tasty addition to potato chips or tempered potato.