Biome changes with height at some decimals if it is close to a full number
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is duplicated by 2
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Since 1.15, biomes in the nether can be three-dimensional, not just two-dimensional, meaning that they can change depending on the height as well. That hasn't been mentioned in any official changelog though.
I believe this bug was resolved incorrectly. It was marked as "works as intended" on the basis that this behavior is intended for Nether biomes.
However, although the screenshots are from the Nether, the bug report itself does not specify the Nether and applies to all dimensions, which is supported by the fact that MC-209700 and MC-238804, both of which concern Overworld biomes, were marked as duplicates of this issue.
According to its patch notes, 21w40a removed non-cave biomes changing by height (the snapshot mostly resolved the issue, but biomes still change by height along their edges as of 1.18 Pre-Release 4). The fact that 21w40a tried to remove this implies that this is unintended for Overworld biomes and thus this feature does not work as intended.
This is what 3D biomes function does