The bug
Dirt can generate naturally on the surface near pools, which is pointless because it ends up becoming grass anyways. This also occurs with lava pools.
Reproduction steps
Note that reproducing this bug seems to be dependent on the order in which chunks are loaded. Therefore you might have to adjust your view distance and don't directly teleport to affected placed. The original reporter used 16 chunk render distance.
Last updated for 21w17a
Seed:
-5208210088792058538
Coordinates:
/teleport -12 76 -544
If you do not see dirt patches at the above location, try teleporting to the following location afterwards:
/execute in minecraft:overworld run tp @s -192.32 66.25 -644.35 -49.20 53.70
Related issues
is duplicated by
Attachments
Comments


Rivers do the same thing. If you have a custom world with the sea level lowered the dry riverbeds are dirt but grass eventually spreads to them (but the spread can only start once a player is close enough, so the player usually arrives early enough to witness it).
In the case of ponds I'm guessing it's so they don't have to specify 2 block types since it picks randomly between stone, sand, and dirt (fun fact: if you create multiple worlds using the same seed one of the few things that will be different is which of these block types a specific pond picked).

I've generated the world multiple times and every time it has been dirt there.

Clones MC-124989. I don't think it was fixed in 1.14.3

This also happens in 1.16.5, despite the attached screenshot.

They took a screenshot of the wrong pool. You can see exposed dirt in the background of the 1.16.5 photograph.

I don't think rivers do the same thing.
Can confirm in 1.17.1.
Caves & Cliffs 1.17.1 Datapack Preview
Seed: 8321433975529524506
Coordinates: /execute in minecraft:overworld run tp @s 128.92 73.51 -492.96 -404.42 48.62

This is fixed in 21w40a