Now, that doesn't necessarily mean there are no recipes for the medium and large ones, we just know that minor ones are not part of the recipe.
While that's true, if you think about it, each plant has its unique crafting property, so the idea that the medium and the large versions would require different plants or ingredients (since there is no "bigger" empty bottle) doesn't sound very convincing.
What is the thinking behind this, if any?
That's another good question. When I posted a topic talking about how useful/useless the Talents are, that question would come up quite a few times. Generally speaking, there are many things in D:OS2 that suggest very bizarre, mind-boggling decision-making. Many things seem like a "rough sketch" that the devs came up with initially but never got around to polishing them later on.
*Hopefully* there is an enhanced edition on the way (chances are good that there is) and most if not all of said things receive an overhaul.
