Item IDs with a underscore dont work

Hello!

I run chained command blocks in my realm to kill off mobs at spawn and destroy their drops.

It all works as intended, with the only exception, that Items with IDs that have an underscore in it dont work. I can f.e. despawn IDs like arrow, bone, string and gunpowder easily with the following command:

kill @e[type=item,name=arrow,r=80]

but it doesnt works when i enter an item ID with an underscore in it like rotten_flesh. nautilus_shell or ender_eye

 

is this a bug or intended, and if intended, why?