I'm trying to make a simple data pack overriding default settings of vanilla dimensions, in this case overriding two files to raise the Nether height up to the build limit. The data pack works correctly, but only if it is added after the world creation. If the data pack is added through the data packs menu prompt while creating a new world, the game crashes with the following error message:

The game crashed whilst exception in server tick loop
Error: java.lang.IllegalStateException: Unregistered dimension type: cgy@74d6d08a

The data pack overrides the following files:

data/minecraft/dimension_type/the_nether.json
data/minecraft/worldgen/noise_settings/nether.json

I'm fairly certain data/minecraft/dimension_type/the_nether.json is the single cause of the crash. Definition for the Nether is overwritten to allow the game to generate new portals above the default 128 blocks logical height.

data/minecraft/worldgen/noise_settings/nether.json is only used to raise the default generator height from 128 blocks up to 256.

The data pack is attached below. I've also recorded the issue:

Crash, adding the pack during world creation

Data pack working correctly, added to an existing world