Mine normally do not confuse the pads with the carpet. We do have accidents, but that is my fault for not getting them out in time. Especially once they have ued them, they can smell the scent - however faint and know where to go.
Oh, I probably should mention that they did confuse them with area rugs, so I have taken up all my area rugs for now.
The washable pads really do save money and most of them work as well if not better than the disposables.
