I loaded up 4 worlds with exactly the same seed and some random trees exist or dont exist, or, in the case of oak trees, are generated in their bigger form. If this happens and how seems to be random. I am unsure if this is a bug ir a feature. My first thoughts were that the game just generates a "forest" with random trees, but a lot of times almost all trees are the same. For example, in the two pictures of the village, the only differences i could find were a tree at the bottom middle and a tree on the middle right that exist in one picture, and don't in another.

Seeds used:

4665803884652228095 for the forest with the plains and the ocean at the bottom right, and

3581145249297584162 for the dark forest with the village, on two differen coordinates.