World Spawn Point does not spawn you at highest possible y axis

In the minecraft PC version, the worldspawn will always spawn one at the highest possible Y-axis. However, I recently learned about a seed called "thrice" for MCPE that actually spawns you in a cave system. This means that the algorithm for the world spawn point is tied to a specific y axis instead of the highest possible y axis.

Here is how to reproduce:

1. Create a new MCPE world
2. Set the seed to "thrice"
3. You will spawn in a cave system