Min. Y -64: Sections starting at 0 and not -64!

[SinanAkkoyun]

I am debugging the issue that mineflayer flatworlds for 1.20.1 do not render at all (but are able to have the click raycast)

I noticed that for all sections of a chunk, the y value starts at 0, not at -64.

(to reproduce, console.log in mineflayer-viewers worker.js:)

function setSectionDirty (pos, value = true) {
  const x = Math.floor(pos.x / 16) * 16
  const y = Math.floor(pos.y / 16) * 16
  const z = Math.floor(pos.z / 16) * 16
  const chunk = world.getColumn(x, z)
  const key = sectionKey(x, y, z)
  // console.log('Chunk:', chunk)
  if(y < 0) {
    console.log(key)
    console.log('Sections:', chunk ? JSON.stringify(chunk.sections) : 'No chunk')
  }

  if (!value) {
    delete dirtySections[key]
    postMessage({ type: 'sectionFinished', key })
  } else if (chunk && chunk.sections[Math.floor(y / 16)]) {
    dirtySections[key] = value
  } else {
    postMessage({ type: 'sectionFinished', key })
  }
}

Now, I already removed every < 0 instance with < -64, loops starting at y 0 -> y -64 and stuff like that, in both prismarine-world (world.js: initialize: if (y >= height || y < -64) { return false }) and mineflayer-viewer (too many to list).

But I don't understand why it simply won't load, but all bot functionalities work!!!

I'd be super grateful for any advice, thanks a lot!