Updating can cause straight biome borders with pale garden

Updating to 1.21.4 has no biome blending applied, sometimes causing straight biome borders at chunk borders.

How to reproduce

1. Set render distance to 2 chunks
2. In 1.21.3: create a new world
   • Creative
   • Seed: 60694719
   • Keep winter drop experiment disabled
3. Don't move and exit the game
4. Update to 1.21.4-pre3
5. Reenter the world
6. Increase render distance and look north-east
7. The biome border is straight

Expected result
The biomes are blended causing non-straight border.

Cause
The data-fixes apply the BlendingDataFix in schema 3441 (first snapshot of 1.20), but it isn't applied in the 1.21.3 -> 1.21.4 update.