Here tea bags always seem to come with much shorter brewing times. So if the pack, nylon or paper, gives shorter than loose leaf brewing time it's dust - not necessarily the estate grade "dust". Perhaps from premium leaves and tips going into the blend, but cut/ground far, far finer than loose leaf.

By the time we get to super-premium, I'd just go loose leaf always. Quite agree nylon is an innovation we shouldn't have. :)