What flavor characteristic often results from brewing tea composed of fannings or dust found in flat bags?

A more bitter, less nuanced brew because they release tannins and caffeine rapidly.

Tea particles classified as fannings or dust, which are commonly found in inexpensive flat tea bags, possess an extensive surface area. This characteristic leads to an extremely fast rate of extraction once exposed to hot water. While this means flavor and color appear quickly, the speed is often too aggressive for desirable flavor development. As a result, the brewing process quickly pulls out high concentrations of bitter compounds, primarily tannins, and caffeine early in the steep time. This rapid dumping of these elements tends to overwhelm or mask the more subtle, desirable flavor oils and complex aromatic notes that characterize high-quality tea, resulting in a brew that tastes predominantly bitter and lacks depth or nuance.