When you crawl into a 1x1 space you can see everything clearly than what you can before

1.17 with the Caves and Cliffs experimental toggle on:

1.18/Caves and Cliffs Part 2:

Steps to reproduce:

1. Get a water bucket
2. Mine a 1x1 tunnel
3. Place the water bucket  and swim into the tunnel
4. Go in 3rd person view

Expected results:
You should see everything clearly as what is shown in the first picture

Observed results:
Every block is black and your camera is confined to a 0.8x0.8 block