The Bug:

The three output slots of the brewing stand's GUI display only a regular bottle/regular potion texture, indecating to the player that only empty bottles, filled bottles, or regular potions can be inserted into the respective slots. This is innacurate, as splash potions and lingering potions can also be inserted into all three slots.

Suggested fix:

GUI's such as the smithing table, cycle through all possible templates, types, and materials allowed in their respective slots. This behavior could be translated over to the brewing stand's output slots to properly convey to the player which items are applicable for insertion.

Screenshots/Videos: