Arrows with effects

Arrows have an effect if used with an /entitydata command

Strange thing, but it happened to me right now.

How to wake up the bug:

1. Get into the Creative world.
2. Put a repeating command block down.
3. put this in /entitydata @e[type=arrow]

{pickup:0}

or /entitydata @e[type=arrow]

{pickup:1}

4. Shoot an arrow