[3.84] open mire tiles under tree lack mossy groundcover

[Galgana]

While exploring open mire terrain, I noticed that marshland tiles in the middle of watery areas did not have moss groundcover when the terrain generated a tree on top. But then I saw some tree-bearing tiles next to water did occasionally have moss.

I'm attaching a set of screenshots taken at 2 different open mire terrains with pine mire on the border.
Non-mossy tiles are highlighted in yellow.

I was wondering whether the absence of moss is an intended effect of the zoom-in map's terrain generation.
It raises an interesting question about the ecological mechanism by which a young spruce, specifically, uses to inhibit moss if such a tree should happen to be standing in waterlogged soil.

[Sami]

It's just so that spruces may generated to shallow water locations.
In these cases the ground has been created in the water for the tree to stand on, but as there is no moss in the water it doesn't appear as a groundcover for these trees.
The locations of the trees standing just next to the water - with no groundcover - have been also water initially.
If considered necessary this could be tidied up so that the trees would appear straight out from the water, with no ground showing at all.

[Galgana]

In these cases the ground has been created in the water for the tree to stand on

Interesting... I suppose that must be the underlying mechanism for the Netherlands-style land reclamation exploit in this old thread!
It's a fun side-effect which several players would sorely mourn the loss of.

If considered necessary this could be tidied up so that the trees would appear straight out from the water, with no ground showing at all.

Now I'm wondering whether a randomly-placed tree may possibly overwrite a spring tile in the current iteration of the terrain generator.
This hypothetical situation could be attributed to bad RNG luck. But I think that accidentally erasing the chance to discover a water source is more saddening than if a player simply failed to notice water tiles which happen to be concealed by the trees or flora growing on top.

[Sami]

In these cases the ground has been created in the water for the tree to stand on

Interesting... I suppose that must be the underlying mechanism for the Netherlands-style land reclamation exploit in this old thread!
It's a fun side-effect which several players would sorely mourn the loss of.

Can be considered loosely related. Building a construction clears the tile, so here it clears the water, and the ground remains.
There's no need to fix this, or some other harmless unintended but fun occurrences, as they don't ruin the usual gameplay.

If considered necessary this could be tidied up so that the trees would appear straight out from the water, with no ground showing at all.

Now I'm wondering whether a randomly-placed tree may possibly overwrite a spring tile in the current iteration of the terrain generator.
This hypothetical situation could be attributed to bad RNG luck. But I think that accidentally erasing the chance to discover a water source is more saddening than if a player simply failed to notice water tiles which happen to be concealed by the trees or flora growing on top.

There are various checks for tree placements so it's not completely random, but I don't remember exactly how spring tiles are included in the checks.
So in theory it might be possible, but the chances are extremely low.