It's the rotation on the planet. It works correctly when I uncheck "Rotate textures with planet" or set the planet rotation to 0. If you don't need that rotation, there's the solution. But that's a bug we'll need to fix.
If you need that planet rotation you may be able to recreate it with a Transform Input Shader between the displacement shaders and the populator, but I would want to move the planet so its centre is at the origin first, as that will allow the transform to be a simple rotation.