If we consider an analogy of paintings, we can imagine that a student or teacher is being given a paintbrush and asked to paint a picture. If we give them a broad brush, such as one they might use to paint the side of a house, then they can only draw out long strokes of paint on the canvas and are unable to add any detail. On the other hand if we give them a very fine brush with just a few hairs in it, they will get caught up in the minutiae and be unable to fill the canvas. Both approaches are wrong by themselves, and I think most reasonable people would want to equip a student with a collection of both wide and narrow brushes. If you look at the structure of the California Science Standards, you will see that the Commission struggled with this issue and resolved it in this reasonable way.
Every standard is organized under the umbrella of a more general concept in science.
Light has a source and travels in a direction. In science you do not get very far if you don't know things. Some of the standards are simple ideas, for example that you could block sunlight to make a shadow. It's almost inconceivable that a typical 8-year old would not have a gut sense about that. Other standards are more subtle, for example the one that says that the color of light striking an object affects how our eyes see it.