How does the introduction of the prediction make things more difficult, as the patter implies?
I've no idea. But I think it might mean that with a prediction, the performer has committed himself to one specific thing.
And there's no gimmicks to hide, because I believe the correct term is "gaff" ;-)
I actually like this one. Though, I would bring the cases out in a stack, and use a Hamman or Vallarino move when placing them out.