Like I said, there is more to it than just belly stripes. I have had normals with the striping as well, but it's not even close. ALL of my het pieds, and possible hets with markers, have the same visual charasteristics added to the striping.
Again I'll ask, why did the largest producer of Pieds in the world hold back all of this possible hets and sell the 100% hets? From what I know, the marker was first discovered by him.
Will some hets not have the marker? Yes. The point is, when buying possible hets, look for the ones with markers and avoid the ones without. Will some normals have markers similar? Yes, but not exactly. It is not just about the stripes.