That would rely on slopes. Not really possible when the zone you're working with is an outcrop pass the vertical base.
It also seems it could also be part of how TG handles geometry. Note this hard transition pyramid with SSS. It's faces are smooth, but when applied a surface layer, it creates subdivided like edges, new faces, basically. Naturally this wouldn't be as viable when the terrain has fine detail and isn't smooth. The cliff I'm working with all has smooth faces, with hard edges, which may just be translating badly with the compute terrain patch size, and planet displacement tolerance. But I'm not sure how to adjust to fix. A smaller patch size gives you better/more faces, but nothing smooth.
Note, the idea here was to create a offset like the remaining plaster on the great pyramids, and than fractalize and vdisp warp the fuzzy zone on Y to mimic the look IRL.