Olivier, I've seen your tut at C3D. I just imported one of the preset terrains that come with GC2, with 2 erosion maps. They are called differently, but when exported, they are 100% the same. And when I use the map as a mixing function in Vue (object parametric), it looks wrong. The masp are supposed to be sediments flows, but when used in Vue, it separates the terrain in two halves upper and lower halves, while the upper half does show some of the sediment, the lower half is wrong, material is applied to both rock and erosion.  The bmp, set to automatic or flat does the same.
I'll try and post some screengrabs later, might be easier for you to see what I mean.