As with others, I've noticed this on an Emerson or two and even the Sebenza I'm carrying today. I wouldn't worry about it.
However, the Emerson Horseman I had had this same slight play except it was while in the closed position. IIRC, the play, while not major, was just enough so that the very tip of the blade would ever so slightly reach above the scales. I think if this were the case it'd be cause for concern.
I always assumed that this was a detent issue rather than a pivot issue. Anyone have any thoughts on that?