This is a minor bug. While in creative mode, the new special arrows (spectre, weakness, poison, etc.) are not infinite like normal arrows or any other item.

Steps to reproduce
1) Go into creative mode.
2) Get a bow and a stack of any of the special arrows.
3) Shoot bow, arrow count depletes.

To be clear, this is just a regular bow, not an infinity bow. It might be WAI but I found it interesting.