HI ,
In the viewport, when viewing vegetation assets from the Library from far away, Twinmotion switches to an LOD version of the asset in order to conserve GPU resources. Without this, scenes could lose performance drastically, or crash outright due to high amounts of high detail vegetation.
While this happens in the viewport, it is not reflective of the exported render, which will render using the higher detail model of the tree assets.
Best,
Raghib