Nether Fossil support islands are sometimes cut off at chunk borders

The bug

Fossiles in the Nether generate with support islands made of soulsand or gravel. Sometimes these islands are cut off exactly at chunk borders.

It appears this issue is still occurring in the latest versions, but not as extreme anymore.

How to reproduce

Last checked for 20w16a

1. Press F3 + G to show chunk borders
2. Create one of these worlds and move to the specified location

   Seed: 5904889398651882482

   /execute in minecraft:the_nether run tp @s 253.29 57.61 570.72 -409.05 46.05