The bug

When re-creating the superflat world, the customize content is lost.

Reproduce steps

1. Create a superflat world in 1.19.3.
   Select Desert Preset Package

   minecraft:bedrock,64*minecraft:deepslate,3*minecraft:stone,52*minecraft:sandstone,8*minecraft:sand;minecraft:desert

2. Creating the World.
3. Open 23w07a version.
4. Click on the world.
5. Click the Re-create button.
6. Click on the World button above.
7. Click the customize button.
8. Customized content is found to be lost and changed to default content.