It doesn’t matter what the base mesh is. Any mesh can be used as a stamp to draw on the terrain like that, because it will draw it from top down.
But if your mesh is not a good fit for drawing into the virtual texture for some reason, then you can add a second mesh such as a plane that has the sole purpose of cheaply drawing into the RVT. This was my suggestion.
Simply spawn the RVT stamp (the plane in the video) at the same XY position as the hole mesh, and then you can draw whatever you want into the RVT from the plane, giving you the ability control the blending independently of the hole mesh.
The plane is then hidden during the main render pass, so you only see the hole mesh and the landscape - but the plane’s contribution to the virtual texture is maintained.
This technique is commonly used to stamp things like roads onto landscapes, and is popular because it is cheaper than decals.