Replicating model viewer lighting In threeJS

Question

I have a threejs scene that I would like to be lit up niceley. I really like the default lights in model viewer. My understanding is that if neither skybox-image or environment-image is specified, default lighting will be applied. If 'neutral' is specified without a skybox, then a more evenly-lit environment is applied instead. Thats great, so I looked at the model viewer code and found this...

export default class EnvironmentScene extends Scene {
  constructor() {
    super();

    this.position.y = -3.5;

    const geometry = new BoxBufferGeometry();
    geometry.deleteAttribute('uv');

    const roomMaterial =
        new MeshStandardMaterial({metalness: 0, side: BackSide});
    const boxMaterial = new MeshStandardMaterial({metalness: 0});

    const mainLight = new PointLight(0xffffff, 500.0, 28, 2);
    mainLight.position.set(0.418, 16.199, 0.300);
    this.add(mainLight);

    const room = new Mesh(geometry, roomMaterial);
    room.position.set(-0.757, 13.219, 0.717);
    room.scale.set(31.713, 28.305, 28.591);
    this.add(room);

    const box1 = new Mesh(geometry, boxMaterial);
    box1.position.set(-10.906, 2.009, 1.846);
    box1.rotation.set(0, -0.195, 0);
    box1.scale.set(2.328, 7.905, 4.651);
    this.add(box1);

    const box2 = new Mesh(geometry, boxMaterial);
    box2.position.set(-5.607, -0.754, -0.758);
    box2.rotation.set(0, 0.994, 0);
    box2.scale.set(1.970, 1.534, 3.955);
    this.add(box2);

    const box3 = new Mesh(geometry, boxMaterial);
    box3.position.set(6.167, 0.857, 7.803);
    box3.rotation.set(0, 0.561, 0);
    box3.scale.set(3.927, 6.285, 3.687);
    this.add(box3);

    const box4 = new Mesh(geometry, boxMaterial);
    box4.position.set(-2.017, 0.018, 6.124);
    box4.rotation.set(0, 0.333, 0);
    box4.scale.set(2.002, 4.566, 2.064);
    this.add(box4);

    const box5 = new Mesh(geometry, boxMaterial);
    box5.position.set(2.291, -0.756, -2.621);
    box5.rotation.set(0, -0.286, 0);
    box5.scale.set(1.546, 1.552, 1.496);
    this.add(box5);

    const box6 = new Mesh(geometry, boxMaterial);
    box6.position.set(-2.193, -0.369, -5.547);
    box6.rotation.set(0, 0.516, 0);
    box6.scale.set(3.875, 3.487, 2.986);
    this.add(box6);


    // -x right
    const light1 = new Mesh(geometry, this.createAreaLightMaterial(50));
    light1.position.set(-16.116, 14.37, 8.208);
    light1.scale.set(0.1, 2.428, 2.739);
    this.add(light1);

    // -x left
    const light2 = new Mesh(geometry, this.createAreaLightMaterial(50));
    light2.position.set(-16.109, 18.021, -8.207);
    light2.scale.set(0.1, 2.425, 2.751);
    this.add(light2);

    // +x
    const light3 = new Mesh(geometry, this.createAreaLightMaterial(17));
    light3.position.set(14.904, 12.198, -1.832);
    light3.scale.set(0.15, 4.265, 6.331);
    this.add(light3);

    // +z
    const light4 = new Mesh(geometry, this.createAreaLightMaterial(43));
    light4.position.set(-0.462, 8.89, 14.520);
    light4.scale.set(4.38, 5.441, 0.088);
    this.add(light4);

    // -z
    const light5 = new Mesh(geometry, this.createAreaLightMaterial(20));
    light5.position.set(3.235, 11.486, -12.541);
    light5.scale.set(2.5, 2.0, 0.1);
    this.add(light5);

    // +y
    const light6 = new Mesh(geometry, this.createAreaLightMaterial(100));
    light6.position.set(0.0, 20.0, 0.0);
    light6.scale.set(1.0, 0.1, 1.0);
    this.add(light6);
  }

  createAreaLightMaterial(intensity: number): MeshBasicMaterial {
    const material = new MeshBasicMaterial();
    material.color.setScalar(intensity);
    return material;
  }

So that I can replicate the lighting in my own scene (not using model viewer) my questions are:

1. What are all the boxes for?
2. With the exception of the point light, all the other "lights" appear to just be meshes with a basic material applied. So how do they help light the scene?

I was expecting to see perhaps an ambient and 2 spotlights or similar.