So it seems
more roundness helps this issue, but I'm still confused why this side of the cube is not responding to displacement at all. You'd think the round borders would be having issues if anything, not the faces.
Compute Terrain is designed for use on a planet. You can use it on other objects, but when you do this the sides of the cube are like the sides of a planet. In these regions, the "up" vector is pointing along X and Z, not Y. So "lateral" means a different thing here. On a face that's pointing along the X axis, X displacements are vertical, not lateral, so they will be cancelled out if you use a feature that cancels out non-lateral displacements.
Furthermore, calculation of normals doesn't work well at the "equator" of the planet where the normals have a Y component of 0, and this is true on the sides of your cube. But I don't know if that's the issue here.
Oh that makes sense, and is actually beneficial to some extent in some scenarios, like I just adjusted me scene for. And yeah I see the difference in lateral and normal, but it does work to still achieve the shaders goal, though, because of orientation, the Y stretching is happening along X it seems (as you mentioned).
Thanks for the quick response.