Basalt pillars can again spawn inside of and replacing parts of nether fortresses

Steps to reproduce:

1. Generate a standard world with the seed “-6984174039507203179”.

2. Enter creative flight.

3. Execute

   /execute in minecraft:the_nether run tp @s 617.37 71.38 -255.23 -404.70 34.35

Observed behavior:

A basalt pillar replaces parts of the wall of a nether fortress.

Expected behavior:

Basalt pillars should not replace parts of other structures.

Note: 20w22a is actually not affected, the label is erroneous.