Iceberg biome glich (incorrect blending between versions)

Steps to reproduce:

1. Somehow open a world with an iceberg biome in 1.21.50 and only load a few chunks. The iceberg biome must still exists in 1.21.73.

2. Update (the game) to 1.21.73 and open the world which was last opened in 1.21.50.

Expected result:

Find the iceberg biome unchanged.

Actual result:

Find frozen plain at the border of the loaded iceberg biome which is blending in the unloaded part of the iceberg biome.

Warning: only tested with the seed 2860514911604195166 at 1300 y -750 since I can’t play 1.21.50 anymore.

My experience:

I reopened a world from 1.21.50 and I went into an iceberg biome that I had previously partially loaded. The world started generating frozen plains to merge the loaded iceberg biome into the unloaded iceberg biome.

You can find a trimmed version of my world below. I used the chunker app to only keep the chunks with my structures in that biome (at 1300 y -750) (and stayed in 1.21.50). You should see the biome glich around it. I also add a screenshot of what my experience.

FIX (luckily for me)

Force the update of the a backup of the world using the chunker app (https://www.chunker.app ) before loading the area again (thus preventing the wrong biome blending). Warning: also breaks biome blending in the rest of the world (which I hope won’t cause me problems somewhere else).