Oh I see, now.
I have to say, a strange feature, that I can't think of any good use for, since it's so prone to so many oddities with even a simple terrain.
I just tried something now, and even trying to do soft snow up close, I found this created issues when I added soft undulation to the terror bird scenes hill (prior to compute terrain), and then had sunken snow melt.
Why doesn't it just revert to the Compute Terrain, and only the "soft version" when the Compute Terrain's smoothing effect is active? Because if I turn on that feature in Compute Terrain, the surfaces match fine. Seems like this "smoothing effect" could just smooth to the computed terrain, and if it is smoothed, to that smoothed terrain. Sure you can mask, but that's a lot of masking of X shaders you're using when it could just work correctly (in my opinion) from the get go and only use smooth if you're actually using it.
Ex. My scene already accounts for how smooth the surface needs to be for smooth snow in the initial terrain geometry, and doesn't need a smoothing effect of the compute terrain, I just need to cut through 14 shaders without having to mask all the surface shaders, plus masking of masks.
This is how I assumed it actually worked, and would be a good feature.