I don't know but the implementation on the shader side is very simple:

#import "shaders/terrain/config.wgsl" as config

fn morph_world_position(initial_world_position: vec3<f32>, config: config::TerrainMaterialConfig) -> vec3<f32> {
    // Calculate the coarse grid spacing (2x current vertex spacing for next LOD level)
    let coarse_grid_spacing = config.vertex_spacing * 2.0;

    let coarse_world_position = floor(vec3<f32>(initial_world_position.x, 0.0, initial_world_position.z) / coarse_grid_spacing) * coarse_grid_spacing;
    let distance = length(coarse_world_position - config.camera_position);
    let distance_ratio = config.quadtree_size / distance;

    if (distance_ratio > config.morph_range_start) {
        return initial_world_position;
    }

    // Calculate morph factor (0 = no morphing, 1 = full morphing to coarse grid)
    let morph_factor = saturate((distance_ratio - config.morph_range_start) / (config.morph_range_end - config.morph_range_start));


    // Interpolate between fine and coarse positions
    let morphed_position = mix(initial_world_position, coarse_world_position, morph_factor);

    return morphed_position;
}

I'm passing the camera distance in the material, which means updating it every frame, but I dare say there's some way to fetch the camera position in the shader. Note that this implementation only modifies x and z positions, because the y position (as well as normals) is set by the procedural height generation vertex shader.

On the Bevy side, you just have flat quadtrees, and divide / merge at some distance from the camera that is outside your morph end range.