I see no duck: https://en.wikipedia.org/wiki/Battle_Chess#/media/File:ST_Ba...

I would consider the possibility that your water-based memory is flawed, and you were already primed to think of a duck by the time you tried to recall the details of the queen's design.

Edit: or this could be an example of the Mandela Effect, and you just switched from a universe where the designer was shocked by their bosses okaying a superfluous duck!

Or it may have been re-added in one of the later versions. I remember there being several full-3D versions of the game (though I don't recall any idea of whether they were officially linked to the original shown here).

More likely it's a false memory created after hearing the duck story.