Asked around in chat about these, general consensus was it is a bug.
Penultimate turn (turn 36) in this battle:
http://replay.pokemonshowdown.com/randombattle-126522847
Background: Omastar had used shell smash earlier in the battle, activating its power herb, so it was item-less. My specs delphox then used switcheroo on omastar.
The result:
Code:
Delphox used Switcheroo!
Delphox switched items with its target!
The opposing Omastar obtained one Choice Specs.
Delphox obtained one Choice Specs.
As you can see, both pokemon received choce specs.
I'm not sure if magician is behind this, but I do not think it should be.