[MC-238682] Magma blocks can generate within ocean monuments

Magma blocks can generate within ocean monuments.

Here is an example:

Version: 1.21.4

Seed: 1428380131082779128
Coordinates: /execute in minecraft:overworld run tp @p 47757 40 62443 180 0

Generate a world with the seed provided above and teleport to the given coordinates.
Look closely at the nearby magma blocks.
Take note as to whether or not magma blocks can generate within ocean monuments.

Magma blocks can generate within ocean monuments.

Magma blocks would not be able to generate within ocean monuments.

Linked issues

Can confirm.

Can confirm in 21w42a.

Can confirm in 1.18 Pre-release 1.

Confirmed in 1.18 full release.

I am also able to confirm this in 1.18.1.

I believe this issue was first introduced in 21w37a due to the change in how magma blocks generate underwater. According to the 21w37a article,

Magma Blocks sometimes generates at the bottom of underground bodies of water

and I'm persuaded to believe that this particular change resulted in this problem occurring.

You can use the information below if you wish to reproduce this in 1.18.1.

[media]

Version: 1.18.1

Seed: 3872443473972444367
Coordinates: /execute in minecraft:overworld run tp @s 5730.32 40.50 -1285.60 556.73 25.74

Can confirm in 1.20.1.