I am glad you found something to try. Let us know if you need any help setting it up.
I agree it would be great to be able to read that information in a material without having a second texture. It comes up frequently among internal artists as well. I think the only thing stopping it, is that it would be hard to check in a partial solution for this, such as one that works with only one heightmap. So the person who writes this feature probably has to handle it working with multiple landscapes and streaming etc so it probably ends up being a lot harder than it sounds at first glance.
Converting landscapes to distance fields also gets requested. I do not believe that feature would be quite as complicated (I have done similar code) but it may be quite slow to generate DF for large landscapes.
For kite demo we briefly had talked about doing it so the landscape could composite into the distance fields and use the ray traced distance field shadows. Instead we ended up with a different feature that fit the performance needs more, a further cascaded shadow region called the FAR shadow that meshes had to set “affect far shadow” to true to affect, and we just had landscape also affect that pass.