Unnatural shape looking like a chunk border but appears to be completely unrelated to chunk borders

The bug

I noticed this weird unnatural shape that looks like a chunk border but it appears to be completely unrelated to chunk borders. This isn't an issue in 1.16.5.

How to reproduce

Seed: -8508883206669806165
Coordinates: /execute in minecraft:overworld run tp @s -756.78 65.00 -1277.73 -49.63 32.73