When importing a custom world generation, in the biomes data field, temperature is written wrong. It's written temparature. Using the correct spelling causes the dimension to be the end's generation with a different lightmap.

https://gist.github.com/RainWarrior/2c32848aad78910a3ca148b82c91f7c2 were the settings used, with a different namespace. It was tested once directly like this, and once with temparature written as temperature in biomes: plains