Suggestion by @anselm (paraphrased)

There could be more detailed docs on why ecs or how the ecs pattern works a bit more philosophically.
In my mind that can be a brief discussion.

I feel like the core pattern of the engine is to encourage developers to use a declarative or data driven pattern for expressing the objects and relationships. The goal is to separate the WHAT from the HOW. And the reason ECS maps well to that is that it encourages granularity.

The difference is pretty clear if you compare a traditional Threejs application (such as building a simple scene) with an ECS approach.
In the former you are mixing two separate things together; you are specifying state AND you are talking to an api.

For example here you focus on both WHAT and HOW:

const scene = new scene()
const camera = new camera()
scene.add(camera)

Whereas in a data driven pattern you're tending to focus just on WHAT:

const elements = [
  { type: scene }
  { type: camera, parent: scene }
]
loadstuff(elements)

Philosophically the latter approach is cleaner.