I was looking at the arrow of slaying magic item and part of it intrigued me (bold for emphasis mine):
Some are more focused than others; for example, there are both arrows of dragon slaying and arrows of blue dragon slaying.
Is there any mechanical benefit from having a more focused arrow?
As it doesn't impact extra damage from the magic of the arrow, I don't get what the advantages would be of having more focused arrows.
The only thing I came up with, is that these arrows are not to be created by players, but more often found as loot/treasures. Given that, a more focused target will restrain the number of situations where the player can use it efficiently.
Is there any benefit I missed?
Note that I am asking about the mechanical benefits that more focused arrows might have over more generic arrows, not about designer reasons for why these kinds of arrows exist.