It isn’t their job to deal with mislabelled or deceptive products. That is typically dealt with by federal, state, and local governments.
It might be be an issue if they were including unlisted ingredients, but questions such as understating the amount of “filler” and implying a product is primarily the “good stuff” and not filler, is not a kashrus agency.
Some of the smaller local hecksherim, that are supervising products for local consumption only, might be more inclined to deal with non-kashrus issue (e.g. the city’s rabbi noticing the the city’s only bakery is using large amounts of “kosher” sawdust to dilute the bread).