It seems they are wanting a blend of stones/bricks/gleam and other materials from a variety of planets, not just the planet you are on or just from all over.
I think it should be how it is used. A tall all blue tower I can see being penalized, but most want a road to be the same, unless the player creates a design in it that is consistent in the whole road, or is trimmed with a different types of whatever from another building material.
There is the aspect that players will have time to make adjustments, this isn’t a race so if for some reason your streets and other builds don’t match what they want you can later make changes.
Maybe while in the hospital you can work on different ideas for some changes, or adding in another area a piece that could be make of various materials? Could be a great distraction.