DynDOLOD\Docs\trees.ultra\DynDOLOD-Trees.html explains 3D tree LOD for LOD level 4 and billboards for the higher LOD levels.
LOD always starts beyond the loaded cells and this applies to near/far grid of dynamic LOD as explained in DynDOLOD_Manual.html.
The near/far grid are just identifiers how far away models show beyond the loaded cells.
For several reasons it makes no sense doing trees as dynamic LOD. One is the large amount of trees and another is the the limited distance.
I use hibryd 3D trees LODs, high rules (tree Static LOD4 | Billboard | Billboard), but I see always 3D LODs.
3D trees LODs is feature with more hit to perfomance, I use EVT, 3D trees LODs hit down my FPS from 100 to 70. I think 3D tree LODs only for 0 level LOD will be better.
P.S. I'm sorry if I don't understand something, but english is foreign language for me.