Bedrock ceiling is exposed in some Nether ravines

Short description of the issue

The bedrock ceiling in the Nether is exposed by some ravines/caves. When the same seed was checked on 26.4 snapshot 5 and earlier releases, the bedrock ceiling was covered by a layer of netherrack.

Steps to reproduce the issue

1. In 26.4 snapshot 6, generate a world with seed: 3041468817867993007

2. Execute this command: /execute in minecraft:the_nether run tp @s 189.82 96.86 332.98 -964.11 -73.95

Expected result

The bedrock ceiling should be concealed by netherrack.

Actual result

The bedrock ceiling is visible.