I made a potion sorter that sorts out only potions from all the items coming into it from a raid farm I made, as the witches drop potions. Unfortunately however, health potions aren't recognized by the brewing stand as an item that can be dropped into it from a dropper, so they do not get filtered properly through the brewing stand. I have not tested this with all different types of potions, so there may be others that are not recognized by the dropper as potions that can be put into a brewing stand.