Hi Rokas,
Had a look into that max file and it doesn't look to be set up any differently than how you'd expect. So basically it's still just tinting the entire object/instance based on a sampled pixel from the map on the surface, instead of doing what we really need which is tinting the individual elements within that scattered object based on the pixel colour beneath that element.
Does that make sense?
Basically if it worked on elements within instances rather than whole instances only it would allow you to scatter huge complex areas and still have tiny level of detail from underlying surface maps.