I will only add my experience. I use a BIAB setup and routinely end up with some trub at the bottom of my fermenter. I use a banjo style screen at the bottom of the kettle and also put a colander style screen across my bucket to catch what the in kettle screen does not. After all this, I still end up with about 1/2 inch or so of sediment at the bottom of my bucket fermenter after everything is done. I am guessing it is some yeast and some "stuff" in the wort. It doesn't bother me as it settles to the bottom of the keg or bottle.