Isn't this a common problem with food in bags, as opposed to hard-sided canisters or other protective containers? I mean, that "dust" is fish food dust, not sawdust or dead human skin.
I've had similar findings with various brands of food...Hikari, NorthFin and others. I always assumed it was just a function of that soft bag being bashed around during shipment, being stacked on store shelves, etc. Since I sometimes spend a disproportionate amount of time with a mortar and pestle...yep, old school all the way...making smaller granulations of food for fry, I am not too bothered by the idea of having some of it pre-crushed for me. But when I do get home with any food in bags, it is immediately subdivided into smaller, tightly-sealed hard containers, either from fish food or sometimes even old peanut butter jars. This not only helps to prevent further smashification, but also keeps the food fresher longer since I only open one and then use it up before moving on to the next.