Deepslate blobs can be generated above Y-level 16 if the blob is 'going upwards'

The bug

According to the 21w13a changelog, deepslate blobs can be generated between Y-level 0 and 16, but if a blob is generated going upwards, the deepslate can be seen in higher Y-levels than 16.

How to reproduce

Seed: -2026412979608502306
Coordinates: /execute in minecraft:overworld run tp @s -382.52 16.05 54.90 -19.80 -30.75