In the Overworld, blocks near the boundaries of biomes may still have blocks directly above or below them which belong to the neighboring biome. Flying up to the sky above these blocks while reading the F3 biome reveals that those columns of blocks next to boundaries consist of a sequence of seemingly random-sized sections corresponding alternatively to both biomes. This is related to the fact that blocks generated at the surface near the boundary may be incorrect: when the two biomes have different surface blocks, some surface blocks from biome A may get into biome B and vice versa.

Expected result: Biomes do not change with height (since that was in the changelog for a 1.18 snapshot I don't remember)

Observed result: Blocks near boundaries of biomes change biome with height.

How to Reproduce: create a default 1.18 RC3 world with seed 2822428772963188543 and watch the plains/beach boundary at spawn (coords: x 300, z -30)