I've create a data pack which uses advancements to detect when a player is in a certain biome, and perform certain actions if they are. Recently while testing however, I found that the data pack will not trigger any actions if the player is above the build limit or below the bedrock layer (bottom build limit).

After checking on the f3 debug screen, I realized that there are no biomes listed when you are above y=319 or below y=-63 in the overworld. I also decided to check if the same occurs in the nether and end, and it does (only difference is that it occurs above y=255 and below y=0) 

What I expected to happen:

Biome below build limit/ above bedrock would extend past build limit/ bedrock layer

What actually happened:

Biomes extend from y= -63 to y=319 in the overworld, but cut off outside of this range. Biomes extend from y=0 to y=255 in the nether/ end, but cut off outside of this range

Steps to Reproduce:

No Biome at Height Limit (overworld) ** 

1. Create a new Minecraft world in 1.18.1
2. Fly or build up to y= 319
3. Jump on top of the block at y= 319
4. Biome in f3 debug screen does not show any biome

No Biome Below Bedrock (overworld)

1. Create a new Minecraft world in 1.18.1
2. Fly or dig down to y= -63
3. Go below y= -63
4. Biome in f3 debug screen does not show any biome

No Biome at Height Limit (nether/ end) ** 

1. Create a new Minecraft world in 1.18.1
2. Go to the nether/ end
3. Fly or build up to y= 255
4. Jump on top of the block at y= 255
5. Biome in f3 debug screen does not show any biome

No Biome Below Bedrock (nether/ end)

1. Create a new Minecraft world in 1.18.1
2. Go to the nether/ end
3. Fly or dig down to y= 0
4. Go below y= 0
5. Biome in f3 debug screen does not show any biome