It seems that River Spring terrain feature spawns some trees, regardless of the type of terrain, which the feature is placed upon. But, it should not have more trees than actual Woodland or Forest tile.

And this tile does not have any tree on it, as its type reads.

However this tile has trees, which is a bit strange.

Sometimes trees spawn on the tiles, where there should not be any tress. I first thought that it could be related to adjacent tiles like Civilization 6 (adjacent Forest tiles affect tree formation on a tile), or general climate of the region, but then there is example like Stone Field example there, which lies right next to it, within the same climate, and with the same adjacent Forest or Woodland tiles. Thus I have deduced that tree spawning scheme is indeed quite inconsistent.

And speaking of Woodland tiles, I searched on Wikipedia to find differences between Woodland and Forest. Here is what I found.

Woodland¹:

    "A Woodland is in the broad sense, land covered with tress, or in a narrow sense, synonymous with wood, a low-density forest forming open habitats with plenty of sunlight and limited shade."

I assume that in Humankind Woodland means a low-density forest. Therefore I think Woodland tiles and Forest tiles should have some obvious distinctive graphical differences, so that one don't have to hover mouse over it to see if it is a Woodland tile or a Forest tile. This problem seems also to be inconsistent. Sometimes it is very easy to distinguish, and sometimes relatively confusing. Here are some examples:

1) https://en.wikipedia.org/wiki/Woodland

I changed the title a little bit to better represent the problem. Also added more screenshots.